words ending with p: * asleep * bishop * buttercup * beep * cheap * chip * cop * creep * clamp * droop * entrap * flop * gyp * gallop * help * heap * hoop * icecap * jump * keep * limp * lamp * lump * makeup * nonstop * outstrip * pump * plump * plop * polyp * primp * quip * recap * snap * strip * scoop * soup * slop * syrup * steep * tulip * teacup * trip * trap * unwrap * weep * warp * worship * whip * yap * zip * zap
Op and Up are the only two (according to the Shorter Oxford Dictionary of the English Language, 5th Ed., 2002.) See: http://www.gps.caltech.edu/~carltape/personal/misc/Scrabble.pdf
up
7 letter words ending in p: * scallop * harelip * airdrop * trollop * bellhop * gumdrop
Words ending with p:asleepatopapprenticeshipbeepbishopbumpbreakupbuttercupbattleshipcampcourtshipcensorshipclumpcoupcopcraftsmanshipcupchirpclampchampcreepcropcroupclipchapchipchopcrimpdampdealershipdraftsmanshipdevelopdollopdripdroopentrapencampenvelopflapfootstepfriendshipflipflopflareupgallopgapgrumpgoopgamesmanshipgovernorshipguardianshipgripgroupgypharelipheaphelphiphubcaphophoophandicaphardshipicecapinstepinternshipjeepjudgeshipjumpkeepleapkinshiplamplimploopleadershiplaplumpmakeupmapmarksmanshipnipnapnightcapnonstopoutstripoverstepownershippeeppartnershippenmanshipplumppoppolypprimpproppumpquipripregroupraindropromprumprevamprecaprooftoprelationshipsoapstoopstripstumpskycapsportsmanshipsalesmanshipstampscoopsnoopsoupshipshopshrimpscrimpslipslopsnapstrapsteepSwapsweepswoopskipscallopseamanshipshowmanshipstewardshipscholarshipsteamshipstopstripsyruptraptiptaptoptriptrumptulipturnipteacuptrooptrollop.unsnapupunwrapwarpweepwhipworkmanshipworshipyapzapzip
asleepbishopburlapdollopencamphiccupicecapmakeupmarkupmishaprecouprevampscrimpshrimpturnipwallopunsnapburlapbarhopbishopcarhopentrapdollopgallophookuphanguplinkuplockupmakeupmarkupmishappileupreshiprevampscrimpshrimpteacupwallop
Partnership
blimpchampchimpchirpclampchompclumpcrampcreepcrimpfrumpgrumpplumpprimppolyprecapskimpsloopsleepslurpstampstripstompstumpslumpswamptramptrumpuncap
up
Some four letter words beginning with P and ending with S:PadsPalsPansPapsParsPassPatsPawsPaysPeasPecsPegsPensPepsPetsPewsPicsPiesPigsPinsPipsPitsPlusPodsPolsPomsPopsPotsProsPubsPudsPugsPunsPupsPuts
peace, piece
zapp
Keep and kelp are four letter words starting with K and ending with P.
Pop, nap, sap, map
papaw, pilaw, pshaw