6 letter words:
butter8,
5 letter words:
brute7,
buret7,
butte7,
rebut7,
tuber7,
utter5,
4 letter words:
brut6,
bute6,
butt6,
rube6,
tube6,
tret4,
true4,
3 letter words:
bet5,
bur5,
but5,
reb5,
rub5,
tub5,
urb5,
ret3,
rue3,
rut3,
tet3,
tut3,
ute3,
2 letter words:
be4,
er2,
et2,
re2,
ut2,