The first thing that comes to mind is all the "un'" words - just think of something negative and put "un" in front of it - unmean, unshy, unangry, etc. But the best "U" word that most people will find very complimentary is "UNIQUE."
· useful
· unselfish
· upbeat
· unassuming
· unbiased
· understanding
adjectives that begin with the letter U areuglyunctuousunderratedundiplomaticunbelievableunstoppableurgentusefuluselessuncomfortableUltraUltraconservativeUltramarineUltramodernUmberUmbilicalUnitedUniversalUnjustUnkindUnknowingUnknownUnlawfulUnlikeUnlikelyUnluckyUnlimited
Umbrella plant, urginea and ursinia are flowers. They begin with the letter U.
Some things that fly that begin with the letter U are:United Airlines airplaneUlysses butterflyUmbrella bird
Some nouns that begin with U are:UgandaukuleleulcerumberumbrageumbrellaumpireuncleundersideunguentunicornunionunitUnited StatesupuproaruraniumurchinurgeurineurnUruguayuserusherUtahUzbekistan
Some things (nouns) that begin with U are:U-boatukuleleumbrellaumpireuncleunderwearunderwriterundertakerunguentunicornupshoturchinurgeurnuserusherUtahutensiluterusutopia
Personal traits that begin with U:UndignifiedUglyUnmanageableUngodlyUninterestingUniqueUrgent
Ugli fruit and uvilla are fruits. They begin with the letter u.
urgency
ullucus
Urchins
Underdog
us