The Collaborative International Dictionary
bog \bog\ (b[o^]g), n. [Ir. & Gael. bog soft, tender, moist: cf. Ir. bogach bog, moor, marsh, Gael. bogan quagmire.]
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A quagmire filled with decayed moss and other vegetable matter; wet spongy ground where a heavy body is apt to sink; a marsh; a morass. Appalled with thoughts of bog, or caverned pit, Of treacherous earth, subsiding where they tread. 
 --R. Jago.
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A little elevated spot or clump of earth, roots, and grass, in a marsh or swamp. [Local, U. S.] Bog bean. See Buck bean. Bog bumper (bump, to make a loud noise), Bog blitter, Bog bluiter, Bog jumper, the bittern. [Prov.] Bog butter, a hydrocarbon of butterlike consistence found in the peat bogs of Ireland. Bog earth (Min.), a soil composed for the most part of silex and partially decomposed vegetable fiber. --P. Cyc. Bog moss. (Bot.) Same as Sphagnum. Bog myrtle (Bot.), the sweet gale. Bog ore. (Min.) - An ore of iron found in boggy or swampy land; a variety of brown iron ore, or limonite. 
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Bog manganese, the hydrated peroxide of manganese. Bog rush (Bot.), any rush growing in bogs; saw grass. Bog spavin. See under Spavin.