Some four letter words with a second letter U are:
spotspamspinspit_______________5 letter words:spellsportspeedspoonspacespill
buttcutecutsgutshutsjutejutsmutemuttnutsputsruts
onus, opus, foul
"WACA " Name of cricket ground in Australia
Chic Ohio
4 letter words, letters 2 and 3 are the same:allybeetbeenbeefbeepbeerbeesboomboonbootcookcoolcoopdeepdeeddeerdoomdoorfeedfeelfeesfeetfoodfoolfootgoodheelhoodhoofhoophootjeepkeepleerloomloonlooplootmeetmoodmoonseedeggsElla
lost post cost host most
Buss (As in BUSS compression) Cuss Fuss
Some three letter words with the second letter W are:awleweoweowlowntwo
Some words that have the second letter U are:augustaurabullbutchercuddlecutdunedurableeuphemismEuropefullfungungutterhurlhutjudgejumpjuryjustkudoslunchluremuchmudmullmurdernudgenullnuptialouchouroutpuddingpunchpushquailquarryquartquartzquoteruderuinrulerushruthlesssuddensuitsullensuppersuretunneltummyturkeyvulnerablevulture
I can only find one in Webster's Second International, and it's an abbreviation: grep '^.of$' /usr/share/dict/words lof
The first one that comes to mind is four; others are:anusaquablueblurboutchugchumclubcluecoupcrudcruxdaubdourdrugdrumfaunfauxfluxfoulglueglumglutgoutgrubhaulhourlaudloudloutmaulnounonusopusovumplugplumpluspoufpourpoutroutscumshunshutslugslumslursmugsmutsnubsnugsoulsoupsourspudtautthudthugthustourtrueyour