一郭[ikkaku] one block
外郭[gaikaku] outer wall (e.g. castle)
外郭団体[gaikakudantai] auxiliary organization
郭公[kakkou] common cuckoo (Cuculus canorus)
胸郭[kyoukaku] chest

五稜郭[goryoukaku] five-sided fortification
城郭[joukaku] fortress
郭公[hototogisu] lesser cuckoo (Cuculus poliocephalus)
遊郭[yuukaku] red light district
輪郭[rinkaku] contour