Dictionary:

bullnose

  (bʊl'nōz')

A rounded edge, corner, or projection, as on a stairstep or paving stone.

1. A blunt or curved outside corner, as the corner made by two walls.
2. A structural member or trim having a rounded edge, as on stair treads, window sills, doors, etc.
3. In plastering, a metal bead used on exterior corners where rounded edges are required.
4. A small, hand-held carpenter’s plane with the cutting edge set near the front of the grip.

The noun has one meaning:

Meaning #1: a small carpenter's plane with the cutting edge near the front
  Synonym: bullnosed plane