'Bittern' definitions:

Definition of 'bittern'

noun

Relatively small compact tawny-brown heron with nocturnal habits and a booming cry; found in marshes

From: GCIDE

Bittern \Bit"tern\, n. [OE. bitoure, betore, bitter, fr. F. butor; of unknown origin.] (Zool.) A wading bird of the genus Botaurus, allied to the herons, of various species. [1913 Webster]
Note: The common European bittern is Botaurus stellaris. It makes, during the brooding season, a noise called by Dryden bumping, and by Goldsmith booming. The American bittern is Botaurus lentiginosus, and is also called stake-driver and meadow hen. See Stake-driver. [1913 Webster]
Note: The name is applied to other related birds, as the least bittern (Ardetta exilis), and the {sun bittern}. [1913 Webster]

From: GCIDE

Bittern \Bit"tern\, n. [From Bitter, a.]
1. The brine which remains in salt works after the salt is concreted, having a bitter taste from the chloride of magnesium which it contains. [1913 Webster]
2. A very bitter compound of quassia, cocculus Indicus, etc., used by fraudulent brewers in adulterating beer. --Cooley. [1913 Webster]

Bittern is found three times in connection with the desolations to come upon Babylon, Idumea, and Nineveh (Isa. 14:23; 34:11; Zeph. 2:14). This bird belongs to the class of cranes. Its scientific name is Botaurus stellaris. It is a solitary bird, frequenting marshy ground. The Hebrew word (kippod) thus rendered in the Authorized Version is rendered "porcupine" in the Revised Version. But in the passages noted the kippod is associated with birds, with pools of water, and with solitude and desolation. This favours the idea that not the "porcupine" but the "bittern" is really intended by the word.