MULTIPLE RWY OP PARALLEL INTERSECTING RWYS. ACR X TKOF CLRNC CANCELED COULD NOT HOLD SHORT OF INTXN RWYS.

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SHORTLY AFTER BEING CLRED FOR TKOF ON RWY 1L AT SFO; A SOMEWHAT UNCLR 'X CANCEL YOUR TKOF CLRNC' WAS HEARD. THE FO IMMEDIATELY ASKED THE TWR IF THEY WANTED ACR X TO ABORT THE TKOF. THE TWR REPLIED IN THE AFFIRMATIVE. THE ABORT WAS INITIATED AT APPROX 80 KTS. A FEW SECONDS LATER TWR ASKED US TO HOLD SHORT OF RWYS 28L/R IF POSSIBLE. WE WERE UNABLE TO HOLD SHORT. IT APPEARED THAT ACFT ON SHORT FINAL TO RWYS 28L/R EXECUTED GARS. TO ME AS A 'LINE PLT' THE WORD 'ABORT' HAS MORE MEANING TO STOP THE ACFT THAN DOES 'CANCEL YOUR TKOF CLRNC;' ESPECIALLY AFTER MY TKOF ROLL HAS STARTED. ALSO ANY HOLD SHORT RESTRS SHOULD BE RADIOED ASAP. AT 80 KTS AND A LONG RWY; THERE DOESN'T SEEM TO BE ANY EMER TO SLAM ON BRAKES AND POSSIBLY SCARE PAX UNLESS YOU KNOW THAT A POSSIBLE CONFLICT IS IMMINENT. SUPPLEMENTAL INFO FROM ACN 251538: I ADVISED TWR THAT WE WERE AT 80 KTS AND DID HE WANT US TO ABORT THE TKOF. HE RESPONDED AFFIRMATIVELY AND SAID TO HOLD SHORT OF RWY 28 IF POSSIBLE. WE HAD USED APPROX 2000 FT OF RWY WHEN THE 'CANCEL TKOF CLRNC' CALL CAME AND AFTER CLARIFY WITH TWR; IT WAS IMPOSSIBLE TO HOLD SHORT. THIS EVENT WAS CONFUSING AS WE WERE NEVER TOLD WHY TO ABORT AND THEREFORE DIDN'T KNOW HOW AGGRESSIVELY TO STOP. WE ASSUMED IT WAS DUE TO LNDG TFC ON RWYS 28L/R AS WE NOTICED 2 GARS OCCURRING THERE. I WAS FURTHER CONFUSED AS TO WHY RWY 1L TFC WAS ABORTING AND RWY 1R TFC WAS CONTINUING TKOF IF THERE WAS A TFC CONFLICT WITH RWY 28L AND/OR RWY 28R. THE FASTEST WAY FOR US TO CLR THE INTXNS WOULD HAVE BEEN TO CONTINUE TKOF. A NEAR MISS OR RWY INCURSION DID NOT OCCUR AND WOULD NOT HAVE OCCURRED IF WE HAD CONTINUED TKOF. IF THE TWR MUST STOP A TKOF THAT IS IN PROGRESS; USE THE TERMINOLOGY '(CALL SIGN) ABORT YOUR TKOF.'