What is "aculeus"

Aculeus \A*cu"le*us\, n.; pl. Aculei. [L., dim. of acus needle.]

1. (Bot.) A prickle growing on the bark, as in some brambles and roses.
   --Lindley.

2. (Zo["o]l.) A sting.

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

1. n. a stiff sharp-pointed plant process

2. a sharp-pointed process especially a sting of a hymenopterous insect