(bug) noun
1. Any of an order (Hemiptera) or suborder (Heteroptera) of terrestrial or aquatic insects with piercing, sucking mouth parts, wingless or with two pairs of wings, the anterior pair typically horny with an apical membranous part, as the stinkbug, squashbug, bedbug. For illustrations see under INSECT.
2. Loosely, any insect or small arthropod.
3. Often plural U.S. Colloq. Any small but troublesome defect in the design, structure, or operation of an instrument, motor, machine, or the like.
4. Slang An enthusiast; a monomaniac.
5. Colloq. A pathogenic microorganism.
6. Colloq. A miniature electronic microphone, used in wiretapping, etc.
— v. bugged, bug·ging v.i.
1. To stare; stick out: said of eyes.
—v.t.
2. Colloq. To fix an electronic eavesdropping device in (a room, etc.) or to a (wire, etc.).
3. U.S. Slang To annoy or anger; also, to bewilder or puzzle.
—to bug off U.S. Slang Go away! Get lost!
— to bug out U.S. Slang To quit, especially hastily or ignominiously. [Origin unknown]

(bug) noun Obs.
A specter; bugbear. [ME bugge scarecrow. Cf. Welsh bwg ghost.]

(bg)
1. A river in southern Ukrainian S.S.R., flowing 532 miles SE to the Black Sea; also Southern Bug. Russian Yuzh·nyy Bug (yzh′nē bk′).
2. A river rising in western Ukrainian S.S.R., flowing about 500 miles NW to form the Poland-U.S.S.R. border: also Western Bug. Russian Za·pad·nyy Bug (zä′pəd·nē bk′).