Definition from Wiktionary, the free dictionary
Origin unknown; perhaps from bole.
bollard (plural bollards)
- (nautical) A strong vertical post of timber or iron, fixed to the ground and/or on the deck of a ship, to which the ship's mooring lines etc are secured
- A similar post preventing vehicle access to a pedestrian area, to delineate traffic lanes, or used for security purposes.
- (pejorative) A stupid or foolish person; one who behaves like or resembles a bollard.
post to secure mooring lines
post preventing vehicles from entering pedestrian area
See also 
- (traffic bollard): cone