BOX
BOXBALL
BOXBALLS
BOXBERRIES
BOXBERRY
BOXBOARD
BOXBOARDS
BOXCAR
BOXCARS
BOXED
BOXEN
BOXER
BOXERCISE
BOXERCISES
BOXERS
BOXES
BOXFISH
BOXFISHES
BOXFUL
BOXFULS
BOXHAUL
BOXHAULED
BOXHAULING
BOXHAULS
BOXIER
BOXIEST
BOXILY
BOXINESS
BOXINESSES
BOXING
BOXINGS
BOXKEEPER
BOXKEEPERS
BOXLIKE
BOXROOM
BOXROOMS
BOXTHORN
BOXTHORNS
BOXWALLAH
BOXWALLAHS
BOXWOOD
BOXWOODS
BOXY

43 words start with BOX.