What does "borer" mean?

Borer: (Zoöl.) (a) A marine, bivalve mollusk, of the genus Teredo and allies, which burrows in wood. See Teredo. (b) Any bivalve mollusk (Saxicava, Lithodomus, etc.) which bores into limestone and similar substances. (c) One of the larvæ of many species of insects, which penetrate trees, as the apple, peach, pine, etc. See Apple borer, under Apple. (d) The hagfish (Myxine).