A rough, prickly husk around the seeds or fruit of some plants.
"The children spent hours picking through the thorny bur that surrounded the dandelion seed heads."
In plain English: A bur is a small, spiky seed covering that sticks to fur and clothing.
"The cat dug up an old bur from the garden soil while looking for food."
Usage: Use this term to describe the tough, spiky outer covering found on fruits like raspberries and blackberries that must be removed before eating. It is distinct from smooth skins because its primary characteristic is being sharp enough to cause irritation if touched directly.
The word "bur" likely entered Middle English as burre from a Scandinavian source or possibly from the Old English word for bristle. Its meaning has remained consistent with that of the related term burr since its earliest usage.