noun
Etymology: yellow (I) + jacket
1. or yellow hornet : any of various small yellow-marked social wasps of the family Vespidae that commonly nest in the ground — compare hornet
2. : any of several Australian eucalypts with yellowish bark: as
a. : yellow box
b. : a red gum ( Eucalyptus rostrata )
3.
[so called from the color of the capsules]
slang : barbiturate 2