A DC8F FLC ASSUMED A 360 CLRNC WAS FOR A TURN; RATHER THAN A HDG ON APCH TO MIA.

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WHILE ARRIVING AT MIA; ACFT WAS VECTORED BY APCH CTL; AND WAS HELD HIGHER THAN NORMAL (8000 FT MSL) WHILE ON DOWNWIND LEG TO RWY 9L. ACFT WAS CLRED TO DSND TO 4000 FT; WHILE ABEAM THE APCH END OF RWY 9L. ACFT WAS THEN VECTORED TO FINAL APCH AND CLRED FOR THE APCH TO RWY 9L. ACFT WAS ALREADY IN LNDG CONFIGN; STILL TOO HIGH AND TOO FAST FOR THE APCH AT THE DISTANCE WE WERE. APCH CTL ADVISED US THAT WE WERE FOLLOWING SMALL COMMUTER 4 MI AHEAD OF US. I REQUESTED A L 360 (THREE SIXTY) TURN FOR ALT LOSS. APCH REPLIED ROGER CLRED L 360 (THREE SIX ZERO) AND I READ BACK; 'ROGER; L 360 (THREE SIXTY).' WE BEGAN OUR L 360 DEG TURN AND WHILE PASSING THROUGH 280 DEGS; APCH ASKED US ABOUT OUR HDG. I REPLIED; 'PASSING THROUGH 280 DEGS.' HE THEN STATED THAT HE WANTED US ON A HDG OF 360 DEGS; AND TO EXPEDITE BACK TO A HDG OF 360 DEGS; WHICH WE DID. WE WERE THEN VECTORED BACK FOR THE RWY 9L APCH WITH NO FURTHER INCIDENT. IN MY OPINION THE CAUSE OF THE PROB WAS THAT THE INITIAL REQUEST; ATC INSTRUCTIONS AND READBACK WERE NOT CLR ENOUGH. THERE IS TOO MUCH ROOM FOR INTERP WHEN PROPER PHRASEOLOGY IS NOT USED. L 360 DEGS DOES NOT NECESSARILY MEAN A L 360 DEG TURN; AND CLRED L 360 DOES NOT NECESSARILY MEAN A HDG OF 360 DEGS. HDG CLRNCS SHOULD BE STATED CLRLY AS HDG 360 DEGS.