1. Awn definition, a bristlelike appendage of a plant, especially on the glumes of grasses

2. Small wingless insect with a long bristlelike tail Familiarity information: Bristletail used as a noun is very rare.

3. Bristletail, (order Archaeognatha), any of approximately 350 species of primitive wingless insects that measure from 5 to 20 mm (0.2 to 0.8 inch) in length when they are fully grown and have three slender bristlelike appendages at the tip of the abdomen