Home › Words › U › underchinunderchinunderchin means the underpart of the chin.EtymologyUnder- + chinnounThe underpart of the chin.e.g.“The others, however, were not much improvement as respects looks: one had a projecting underchin, the other a very broad face, and the three were anything but pleasing in appearance.” — 1885, Edward Sylvester Ellis, Ned in the block-house, page 163:Definitions & examples from Wiktionary (CC BY-SA 3.0).