PLT OF C172 DECIDES THAT A HOLD SHORT INSTRUCTION FROM GND CTL IS A CONDITIONAL CLRNC AND CONTINUES TAXI AT HIS DISCRETION.

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AFTER RECEIVING MY IFR CLRNC; I REQUESTED MY TAXI CLRNC. THE CTLR ISSUED AN INSTRUCTION TO HOLD SHORT OF THE SEAPLANE LANE (SEALANE) FOR TFC; THEN TAXI TO RWY 35L. I READ BACK THE CLRNC AND BEGAN THE TAXI. (NOTE: MUCH OF THE MOVEMENT AREA IN QUESTION IS NOT CTLED BY GND -- EVEN THOUGH THEY GIVE CLRNCS.) AS I TAXI TOWARDS THE SEALANE; I SEE ANOTHER ACFT COME AROUND THE CORNER FROM THE SEALANE AREA. I ASSUMED THIS WAS THE TFC. AFTER ALLOWING THE TFC TO PASS; I PROCEED ONWARD. AS I AM ABOUT TO PASS THE RWY 17L APCH LINE; THE GND CTLR ASKED ME TO 'STOP.' I WAS ASKED TO CALL THE TWR AFTER MY TRIP. UPON CONTACTING THE TWR; I WAS ASKED WHAT HAPPENED. I EXPLAINED THAT I THOUGHT HE WAS REFERRING TO THE TFC COMING AROUND THE BEND THAT I HAD HELD FOR. HE EXPLAINED THAT IN FACT HE HAD A SEAPLANE AIRBORNE AT THE TIME. HE ASKED ME TO ALWAYS ASK IN THE FUTURE IF THERE'S ANY DOUBT. IN RETROSPECT; WHILE I WILL ALWAYS ASK TO BE SURE; I THINK HOLD SHORT INSTRUCTIONS SHOULD BE QUITE SPECIFIC AND INCLUDE SPECIFIC CONDITIONALS AS TO WHEN TO PROCEED SO THERE'S NO AMBIGUITY. THIS WOULD PREVENT A SIMILAR SIT FROM REOCCURRING.