CTLR TELLS ACR TO 'EXPECT' TO CROSS INTXN AT 10000 FT. PLT DOESN'T HEAR 'EXPECT' AND STARTS DSCNT RESULTING IN LTSS.

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ACR X WAS DSNDING TO FL240 ON THE MEINZ ARR TO MSP. ACFT WAS ISSUED 17000 FT WITH AN EXPECT PEPPR AT 10000 FT. PLT READ BACK DSND TO 17000 FT; CROSS PEPPR AT 10000 FT. I DID NOT CATCH ERRONEOUS READBACK. LATER; ACR X WAS ISSUED 16000 FT. PLT READ BACK AND ASKED IF WE STILL WANTED PEPPR AT 10000 FT. WE REPLIED AFFIRMATIVE; THINKING PLT JUST DROPPED WORD 'EXPECT.' WHEN ACR X DSNDED BELOW 16000 FT CONFLICT ALERT ACTIVATED WITH AN ACFT LEVEL AT 6000 FT. I THEN TRIED TO FIGURE OUT WHY CONFLICT ALERT HAD ACTIVATED. AFTER I REALIZED THIS ACFT WAS NOT A FACTOR; I THEN SAW THAT ACR X WAS OVERTAKING A TURBOPROP; ACR Y. I THEN TRIED TO ISSUE ALTS TO MAINTAIN SEPARATION BUT WAS UNABLE. AS SEPARATION WAS LOST; CONFLICT ALERT ACTIVATED. SUPPLEMENTAL INFORMATION FROM ACN 255995: ON MEINZ 6 ARR INTO MSP; I WAS GIVEN A SPD REDUCTION TO 260 KTS; AND A DSCNT FROM 25000 FT TO 17000 FT WITH A RESTR TO CROSS PEPPR INTXN AT 10000 FT. THE FO READ BACK THE CLRNC TO 'MAINTAIN 17000 FT; CROSS PEPPR AT 10000 FT.' WHILE DSNDING THROUGH 18500 FT; THE CTLR TOLD US TO MAINTAIN 16000 FT. THE FO RESPONDED 'MAINTAIN 16000 FT; DO YOU STILL WANT US AT 10000 FT AT PEPPR?' CTLR RESPONDED 'AFFIRMATIVE.' FO; 'ROGER; WE'RE CONTINUING OUR DSCNT.' AT 13200 FT THE CTLR TOLD US TO MAINTAIN 14000 FT. I INFORMED THE CTLR; THROUGH THE FO; 'WE'RE AT 13200 FT; DO YOU WANT US TO CLB BACK TO 14000 FT?' CTLR'S RESPONSE: 'DSND TO 10000 FT; EXPEDITE YOUR DSCNT.' CTLR THEN INSTRUCTED ANOTHER ACFT TO CLB TO 14000 FT IMMEDIATELY. UPON LNDG MSP; I CALLED INSPECTOR AND SPOKE WITH A SUPVR TO GET CLARIFICATION ON WHAT HAD OCCURRED. I WAS ADVISED BY THE SUPVR THAT OUR INITIAL CLRNC WAS TO DSND TO 17000 FT AND EXPECT TO CROSS PEPPR AT 10000 FT. HE THEN INFORMED ME THEY WERE PULLING THE ATC TAPES TO FIND OUT EXACTLY WHAT TRANSPIRED. AFTER REVIEWING THE TAPES; SUPVR INDICATED THE CTLR ISSUED THE INSTRUCTION TO 'EXPECT TO CROSS PEPPR AT 10000 FT.' HOWEVER; THE FO READ BACK THE DSCNT CLRNC TO CROSS PEPPR AT 10000 FT AND WAS NOT CORRECTED BY THE CTLR. BECAUSE OF THIS BREAKDOWN IN COM; MY ACFT CAME WITHIN 4.6 MI OF A 2ND ACFT. THE SUPVR ALSO INDICATED THAT THIS WAS A CTLR ERROR AND WOULD BE HANDLED INTERNALLY. I FEEL THAT THE USE OF THE TERM 'EXPECT' CAN CAUSE CONFUSION AND LEAD TO MISINTERP IF NOT CORRECTLY ASSIMILATED BY BOTH PLT AND CTLR.