There are tens of thousands of words that have U as the second letter. If you have a specific length of word in mind it would be possible to give you a list.
bull, dull, full, gull, gulf, hulk, lull, mull, mule, null, pull, rule
Audibly is a seven letter word that has u as the second letter and i as the fourth letter.
zulu, guru, juju, mumu
Four-letter words that have "A" as their second letter and "N" as their third letter: band, bans, land, pans, pant, rant, sand, sans, tans, wand, want.
ahem, chez, phew, shed, they, when, them
Four letter words with X as the third letter:boxyfoxyluxenextpoxysexytaxitextwaxy
gain.
Skin
Some four letter words with O as the third letter are:aloeanonatomblobblotblowbookboomboonboorbootbrowbuoychopchowclodclogclotcloycookcoolcropdoomdoordropflogflopflowfoodfoolfootfrogfromglowgoodgoofgrowhoodhoofhookhoopiconidolironknobknotknowlionlookloomloonmeowmoodmoonmoormootneonnookoboeplodplotplowploypoofpoohpoolpoorprompropprowroofroomrookrootscowshodshopshotshowslopsmogsnobsoonsootspotstopthoutooktoottrodtrotuponwhoawhomwoodwoofwoolzoom
cats
baht
armybombcomecomacamedamedimedomefamefumegamehomelamelimelimbLimalimolamalimymamamemomimenamepumaRomesamesometimetame
tree
Some seven letter words with the second letter A and the third letter U are:bauxitecausticcautiondauphinhaughtyhauntedhauteurlaundrymaudlinnaughtypaunchyraucousraunchysauntersausagevaulted
WIND