The Collaborative International Dictionary
Subtriangular
Subtriangular \Sub`tri*an"gu*lar\, a.
Nearly, but not perfectly, triangular.
--Darwin.
Wiktionary
subtriangular
a. (context botany anatomy English) Somewhat triangular
Usage examples of "subtriangular".
It is probable that the subtriangular figure below is intended for the head, as the two circles with central dots are good representations of eyes.