From The Collaborative International Dictionary of English v.0.48 [gcide]: Cupule \Cu"pule\ (k?"p?l), n. [See Cupola.] 1. (Bot.) A cuplet or little cup, as of the acorn; the husk or bur of the filbert, chestnut, etc. [1913 Webster] 2. (Zool.) A sucker or acetabulum. [1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
cupule
n 1: cup-shaped structure of hardened bracts at the base of an
acorn [syn: cupule, acorn cup]
2: a sucker on the feet of certain flies