The Collaborative International Dictionary
Umbonate
Umbonate \Um"bo*nate\, Umbonated \Um"bo*na`ted\, a. [NL. umbonatus. See Umbo.] Having a conical or rounded projection or protuberance, like a boss.
Wiktionary
umbonate
a. (context mycology of a mushroom etc English) Having an umbo
Usage examples of "umbonate".
It is from 1 to 2 inches broad, fleshy, tough, convex, then plane, somewhat umbonate, even, smooth, slightly striate at margin when moist.