6 letter words:
butter8,
gutter7,
5 letter words:
brute7,
buret7,
butte7,
rebut7,
tuber7,
utter5,
4 letter words:
berg7,
burg7,
grub7,
brut6,
bute6,
butt6,
rube6,
tube6,
grue5,
trug5,
urge5,
tret4,
true4,
3 letter words:
beg6,
bug6,
bet5,
bur5,
but5,
reb5,
rub5,
tub5,
urb5,
erg4,
get4,
gut4,
reg4,
rug4,
teg4,
tug4,
ret3,
rue3,
rut3,
tet3,
tut3,
ute3,
2 letter words:
be4,
er2,
et2,
re2,
ut2,