'Humpback' definitions:

Definition of 'humpback'

noun

An abnormal backward curve to the vertebral column [syn: kyphosis, humpback, hunchback]

noun

A person whose back is hunched because of abnormal curvature of the upper spine [syn: humpback, hunchback, crookback]

noun

Large whalebone whale with long flippers noted for arching or humping its back as it dives [syn: humpback, humpback whale, Megaptera novaeangliae]

From: GCIDE

Humpback \Hump"back`\, n. [Cf. Hunchback.]
1. A crooked back; a humped back. --Tatler. [1913 Webster]
2. A humpbacked person; a hunchback. [1913 Webster]
3. (Zool.) (a) Any whale of the genus Megaptera, characterized by a hump or bunch on the back. Several species are known. The most common ones in the North Atlantic are Megaptera longimana of Europe, and {Megaptera osphyia} of America; that of the California coasts is Megaptera versabilis. (b) A small salmon (Oncorhynchus gorbuscha), of the northwest coast of America; the humpbacked salmon. [1913 Webster]