Blue bonnet \Blue" bon`net\ or Blue-bonnet \Blue"-bon`net\, n. 1. A broad, flat Scottish cap of blue woolen, or one wearing such cap; a Scotchman. 2. (Bot.) A plant. Same as {Bluebottle}. 3. (Zo["o]l.) The European blue titmouse ({Parus c[oe]ruleus}); the bluecap.