Natch \Natch\, 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.

Source: Webster's Revised Unabridged Dictionary (1913)