Air carrier First Officer reported during taxi another taxiing aircraft came close to colliding with them. The other aircraft stopped abruptly to avoid a collision.

Narrative

Aircraft X from ORD to ZZZ. Left gate XX at XA:14. Outbound ground control instructed us to taxi to 22L via bravo and victor. From the west line; we understood our clearance to mean we taxi straight out alpha-seven and then turn left onto bravo. As we approached bravo; the aircraft in front of us stopped in the bravo-one intersection; preventing us from establishing. However; we had already began to enter taxiway bravo at this point. We did not expect the aircraft in front of us to stop; but these procedures are normal at ORD. Had we been given instruction to hold short of bravo; we would have stopped well before we did; however at this time there was adequate space between us and the aircraft in front of us at bravo-one; and no other traffic in the area was a factor for us as we were clear to the right on taxiway bravo. As we waited for the aircraft in front of us to move; the captain turned off the nose gear light. When the preceding aircraft moved forward and was no longer a factor for us; the captain turned on the nosewheel light; and we began to move forward to establish onto bravo. As I glanced to the right to make sure we were clear for our left turn; I noticed Aircraft Y to our right taxiing eastbound on bravo at a rate of speed that did not indicate they intended to follow us. This aircraft was not previously a factor; however in the amount of time we sat waiting for the aircraft in front of us to move; Aircraft Y had travelled close enough to us to be a threat. The captain noticed the oncoming aircraft at the same time I did and stopped our aircraft immediately. The stop was not violent or abrupt as we had been moving for only a second and covered no significant distance; a few feet at most. At this point; we were still on taxiway alpha-seven; with a small part of our aircraft protruding onto taxiway bravo. From my right; I could see the oncoming aircraft with all of its taxi lights on; moving towards us. They seemed to be accelerating and mine and the captain's alarm at the situation increased. As the aircraft neared us; I thought that they did not see us; since we were moved up so far that they could not be certain their wing would clear our nose; even if they did see us. The captain began flashing the wing inspection lights to make our aircraft more visible. I contemplated keying my mic to say something to the other aircraft; but felt it wiser not to given the amount of other aircraft on the frequency; and the possibility that the aircraft approaching us was tuned to inbound ground. As I debated keying up; we noticed Aircraft Y decelerate and come to a stop; just short of our position. Their rate of deceleration was such that their nose was moving up and down as the nose gear strut extended and contracted a few times; and we noticed smoke coming from their main gear area. From our vantage point now; we could see that Aircraft Y's left wingtip would have cleared our nose by less than five feet if they continued to taxi.Immediately after they stopped; the controller told Aircraft Z to give way to us; and again instructed us to taxi to 22L via bravo and victor. From the relative positions of both aircraft; we were able to safely make the left turn onto bravo with wingtip clearance; but the Aircraft Z was so close to us that it was uncomfortable being that close on a taxiway. Had the other aircraft stopped a few seconds after they did; we would have had to shut down and be pushed back by a tug. Reflecting on this event; I believe the taxi procedures at ORD to be the main causal factor. It is common at this airport to be given a set of taxi instructions and having other aircraft cross the taxi route a plane is cleared on or be required to join a taxiway behind another aircraft; with no explicit instructions from ground control. This is further complicated by inbound and outbound aircraft using the same taxiways but different frequencies. Taxi technique at ORD relies on pilots seeing other moving aircraft and silently alleviating potential conflicts before they escalate to the point where controller intervention is required. With this in mind; pilots routinely have to interpret their set of taxi instructions in the context of the environment around them to determine how to proceed and who to give-way to. We did not expect to have to stop on taxiway alpha-seven; but as our cleared taxi route was blocked; we were required to. Once our taxi route was clear in front of us; we assumed we could continue moving forward since we were cleared to use bravo taxiway; however an aircraft moving quickly at us from the right gave us pause. We determined the safest course of action was to hold position to avoid a collision with the oncoming aircraft; but given the absence of explicit instructions from a controller; we--and likely the pilots of the other aircraft--lacked a full understanding of the sequence and who was supposed to go first. It is likely that the controller did not anticipate a traffic conflict at the intersection; or that if they did; they figured that we would sort it out on our own.Regardless of sequence or who had the right of way onto taxiway bravo in this scenario; our aircraft was in a position at the intersection of alpha-seven and bravo that would prevent an aircraft from safely passing in front of us. Since we were not instructed to hold short of bravo; we followed the plane in front of us; and in the time that we were stopped; Aircraft Y became a factor. Their rate of speed and the fact that they did not stop until they were very close to us was serious cause for alarm in our flight deck. No instructions from ATC were violated; however the reliance on pilots to mitigate conflicts on their own while on the taxiways nearly resulted in a collision. I believe Aircraft Y did not see us since our lights may have blended in with the terminal lights in the background; but their taxi speed seemed excessive from our vantage point; especially when taxiing through an area where it is common to have aircraft joining and crossing taxiways without them being pointed out by ATC.