Sting, to a zoologist

• A sharp-pointed process especially a sting of a hymenopterous insect
• A stiff sharp-pointed plant process

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Aculeus \A*cu"le*us\, n.; pl. Aculei . [L., dim. of acus needle.] (Bot.) A prickle growing on the bark, as in some brambles and roses. --Lindley. (Zo["o]l.) A sting.

WordNet Word definitions in WordNet
n. a stiff sharp-pointed plant process a sharp-pointed process especially a sting of a hymenopterous insect

Wiktionary Word definitions in Wiktionary
n. 1 (lb en botany) A prickle growing on the bark, as in some brambles and roses. 2 A sting.