FLC RECEIVES CONFUSING TAXI CLRNC.

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DURING TAXI OUT OF STL; ATC ISSUED A CLRNC THAT WAS PARTIALLY BLOCKED. THE XMISSION WE HEARD WAS 'R TURN ON TXWY PAPA AND THEN WAIT FOR AN OPPOSITE DIRECTION CHALLENGER TO CROSS; THEN CONTINUE TO RWY 30R.' WE WERE HOLDING SHORT OF RWY 30L AT TXWY N AT THE TIME. THE CAPT AND I BOTH LOOKED AT EACH OTHER AND QUESTIONED IF WE WERE 'CLRED TO CROSS RWY30L.' I MADE THE CALL TO GND TO VERIFY IF WE WERE INDEED 'CLRED TO CROSS RWY 30L.' THE CTLR QUICKLY RESPONDED IN A RATHER ANNOYED TONE STATING; 'YES; COMPANY X CROSS RWY 30L AT NOVEMBER; R TURN ON TXWY P AND WAIT BY TXWY R FOR AN OPPOSITE DIRECTION RJ TO CROSS AND THEN CONTINUE TO RWY 30R.' I READ BACK THE CLRNC AS BEST AS I COULD; BUT WAS CONFUSED WITH THE CTLR'S PHRASEOLOGY OF 'WAIT BY TXWY R FOR OPPOSITE DIRECTION TFC.' AT THIS TIME WE WERE HDG N ON NOVEMBER; THE RJ TFC WAS OUT OF SIGHT; POINTING S ON SIERRA N OF TXWY P. AS WE APCHED TXWY R; ATC CLRED AN ACR XXX MD80 TO CROSS RWY 30L AT TXWY R WITHOUT DELAY BECAUSE AN ACFT WAS ON SHORT FINAL FOR RWY 30L. ATC ALSO STATED THAT HE WOULD BE FOLLOWING COMPANY AHEAD AND TO YOUR LEFT TO RWY 30R (US). THE CAPT SLOWED DOWN PRIOR TO TXWY R BECAUSE THE MD80 WAS CLEARING RWY 30L RATHER QUICKLY. AT THIS TIME; I SPOTTED THE RJ THAT WAS STILL PARKED ON SIERRA N OF TXWY P. WE BOTH CAME TO THE CONCLUSION THAT THE RJ WAS GOING TO CROSS TXWY P; S ON SIERRA TO RWY 30L. WITH THAT IN MIND AND THE MD80 GIVEN CLRNC TO FOLLOW US TO RWY 30R; WE CONTINUED TO RWY 30R PASSING INTXN TXWY R AND TXWY P. THIS IS WHEN GND CAME ACROSS WITH A RATHER INAPPROPRIATE COMMENT; 'COMPANY X (US); HOW IS THAT RJ SUPPOSED TO TAXI THROUGH YOU ON TXWY P?' I RESPONDED WITH 'WE'RE SORRY; WE THOUGHT THE RJ WAS GOING TO 'CROSS' IN FRONT OF US TO RWY 30L.' THE CTLR THEN STATED 'COMPANY; JUST CONTINUE.' IT TOOK US ALMOST 1/2 THE FLT FROM STL TO DTW TO FINALLY REALIZE WHAT THE CTLR HAD INTENDED TO HAPPEN. IF THE CTLR WOULD HAVE USED STANDARD PHRASEOLOGY AND SAID 'CROSS RWY 30L AT TXWY N; R ON TXWY P AND HOLD SHORT OF TXWY R' THE SIT WOULD HAVE BEEN DIFFERENT. WE WOULD BOTH HAVE KNOWN WITHOUT A DOUBT WHAT OUR TAXI INSTRUCTIONS WOULD HAVE BEEN. THE CTLR'S USE OF NONSTANDARD PHRASEOLOGY AND SOMEWHAT AMBIGUOUS INSTRUCTIONS FORCED US TO TRY AND GUESS WHAT THE CTLR REALLY WANTED. WE GUESSED WRONG. IN THE FUTURE; THE WISEST THING TO DO WITH AN ANNOYED CTLR; BUSY FREQ AND AMBIGUOUS INSTRUCTIONS WOULD BE TO CROSS THE ACTIVE RWY AND SET THE PARKING BRAKE UNTIL THE ENTIRE CLRNC CAN BE VERIFIED.