RWY INCURSION BY THE FLC OF A B727-200 WHEN THE PIC ASSUMES THE CLRNC AS READ BY THE CTLR MEANT THAT THEY WERE CLRED INTO POS AND HOLD AT GSO; NC.

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WE LEFT THE GATE ABOUT 15 MINS PRIOR TO OUR 'WHEELS-UP' TIME. GND ASKED US TO WAIT ON TXWY A. JUST SHORT OF TXWY K; NEAR THE APCH END OF RWY 5. AT APPROX OUR WHEELS-UP TIME; WITH 1 ACFT ABOUT TO TOUCH DOWN; WE WERE INSTRUCTED 'YOU CAN TAXI TO RWY 5 NOW.' IN THE CONTEXT OF WHERE WE WERE; BOTH I AND MY SO (INCORRECTLY) INTERPRETED THIS AS AN INSTRUCTION TO TAXI ONTO RWY 5 FOR IMMEDIATE RELEASE. FORTUNATELY; THE FO POINTED OUT MY ERROR JUST AS I CROSSED THE HOLD SHORT LINE AND I BROUGHT THE ACFT TO A STOP WITHIN A FEW FEET. CONTRIBUTING FACTORS: WE WERE ALREADY SO CLOSE TO THE RWY THAT A CLRNC TO TAXI TO IT SEEMED REDUNDANT. WE HAD BEEN HOLDING SO LONG AT THE END OF THE RWY WITH NO TFC ON THE FREQ THAT I HAD FORGOTTEN THAT WE WERE STILL ON GND CTL. BECAUSE OUR WHEELS-UP TIME HAD JUST ARRIVED; I WAS EXPECTING A CLRNC TO 'TAXI INTO POS AND HOLD.' TO PREVENT A RECURRENCE: I WILL LISTEN MORE CAREFULLY IN THE FUTURE; BEING ALERT FOR MISPERCEPTIONS CAUSED BY 'EXPECTANCY.' GND CTL MIGHT HAVE USED THE TERMINOLOGY 'TAXI UP TO AND HOLD SHORT OF RWY 5;' WHICH WOULD HAVE ELIMINATED ANY CHANCE OF MISPERCEPTION ON MY PART. SUPPLEMENTAL INFO FROM ACN 563028: APCHING OUR ETO; GND SWITCHED US TO TWR; WHO INSTRUCTED 'CLRED TO RWY 5.' AS SOON AS I (COPLT) REALIZED CAPT'S MISUNDERSTANDING; I COMMANDED HIM TO STOP THE ACFT IMMEDIATELY. I CALLED TWR TO TELL THEM OF OUR POS; AND THEY WERE NOT CONCERNED AS THERE WAS NO TFC FOR RWY 5. THIS INCIDENT ITSELF IS BENIGN; BUT ILLUSTRATES THE PROB OF RECEIVING A CLRNC WITH NON-STANDARD PHRASEOLOGY (SHOULD HAVE BEEN: 'TAXI UP TO AND HOLD SHORT OF RWY 5'). WHILE EXPECTING TO HEAR SOMETHING ELSE ('TAXI INTO POS AND HOLD RWY 5). THE PHRASE 'CLRED TO RWY 5' DIRECTLY CONTRIBUTED TO THE CAPT'S MISUNDERSTANDING.