adamant
adamantine
bullheaded
closed to
headstrong
immovable
immutable
impersuadable
impersuasible
impervious
inductile
inelastic
inextensible
inextensile
inextensional
inflexible
intractable
intractile
irresilient
mulish
nonelastic
nonstretchable
obstinate
perverse
pigheaded
self-willed
stubborn
unalterable
unamenable
unbending
unextendible
unextensible
unflexible
ungiving
unimpressionable
uninfluenceable
unlimber
unmalleable
unmovable
unpersuadable
unpliant
unreceptive
unresponsive
unsuggestible
unsusceptible
unswayable
untractable
unyielding
achy
brush-like
clumsier
cur'ous
deckle-edged
farfetched
greenish-gray
icy-cold
indepth
jointless
letter-writing
martial-looking
performative
pseudo-scientific
saddle-sore
sail-like
spaced-out
spikey
standoffish
stodgy
stone-dead
straight-back
weatherly
yellow-black