The Collaborative International Dictionary
Hyporhachis
Hyporhachis \Hy`po*rha"chis\, n.; pl. Hyporhachides. [NL., fr. Gr. "ypo` beneath + ? spine.] (Zo["o]l.) The stem of an aftershaft or hypoptilum. [Written also hyporachis.]
Wiktionary
hyporhachis
n. (context zoology English) The stem of an aftershaft or hypoptilum.