拳固 is read as げんこ (genko) and means fist.
げんこ
genko
げんこつ
(clenched) fist
けんじゅう
pistol
こぶし
fist
けんぽう
kenpō (martial arts)
けんとうせんしゅ
boxer
けんとうか
けんだい
fist-sized
がんこ
stubborn
けんご
solid
ぎょうこ
coagulation
たてしほうがため
tate-shiho-gatame (judo)
ようじんけんご
very cautious (watchful, vigilant)