Merriam-Webster's Collegiate Dictionary:
trim size
trimaran
trimble
trimer
trimeric
trimerous
trimester
trimeter
trimethoprim
trimly
trimmer
trimming
trimness
trimonthly
trimorphic
trimotor
trimurti
trinacria
trinacrian
trinal
trincomalee
trine
trine immersion
trinidad
trinidadian
trinitarian
trinitarianism
trinitrotoluene
trinity
trinitytide
trinket
trinketry
trinocular
trinomial
trinucleotide
trio
triode
triol
triolet
triose
trioxide
trip
trip the light fantastic
trip wire
trip-hammer
trip-hop
tripack
tripartite
tripe
triphenylmethane
triphosphate
triphosphopyridine nucleotide
triphthong
triphthongal
tripinnate
tripinnately
triplane
triple
triple bogey
triple bond
triple counterpoint
triple crown
triple jump
triple jumper
triple play
triple point
triple sec
triple threat
triple-bogey
triple-decker
triple-double
triple-header
triple-space
triple-team
triple-threat
triple-tongue
triplet
tripletail
triplex
triplicate
triplication
triplicity
triploblastic
triploid
triploidy
triply
tripod
tripodal
tripoli
tripolis
tripolitan
tripolitania
tripolitanian
tripos
tripper
trippingly
trippy
