The Collaborative International Dictionary
Natch bone
Natch \Natch\ (n[a^]ch), n. [OF. nache fesse, LL. natica, from L. natis the rump, buttocks. Cf. Aitchbone.] The rump of beef; esp., the lower and back part of the rump.
Natch bone, the edgebone, or aitchbone, in beef.