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The act of increasing by natural growth; esp. the increase of organic bodies by the internal accession of parts; organic growth. Arbuthnot.

Sourness of taste, with bitterness and astringency, like that of unripe fruit.

A river in the Nether World or infernal regions; also, the infernal regions themselves. By some of the English poets it was supposed to be a flaming lake or gulf. Shak.

Of or pertaining to Acheron; infernal; hence, dismal, gloomy; moribund.

ving the taste of vinegar: as, acid fruits or liquors. Also fig.: Sour-tempered. He was stern and his face as acid as ever. A. Trollope.

Full of small kernels like a grape.

Having no seed lobes, as the dodder; also applied to plants which have no true seeds, as ferns, mosses, etc.

s of hearing, or the science of sounds; auditory. Acoustic duct, the auditory duct, or external passage of the ear. -- Acoustic telegraph, a telegraph making audible signals; a telephone. -- Acoustic vessels, brazen tubes or vessels, shaped like a bell, used in ancient theaters to propel the voices of the actors, so…

-- followed by in, formerly also by with and to. They were compelled to acquiesce in a government which they did not regard as just. De Quincey.

The quality of being acrid or pungent; irritant bitterness; acrimony; as, the acridity of a plant, of a speech.

Sharpness or severity, as of language or temper; irritating bitterness of disposition or manners. John the Baptist set himself with much acrimony and indignation to baffle this senseless arrogant conceit of theirs. South.

A plant of the highest class of cryptograms, including the ferns, etc. See Cryptogamia. The Age of Acrogens (Geol.), the age of coal plants, or the carboniferous era.

Gesticulation; the external deportment of the speaker, or the suiting of his attitude, voice, gestures, and countenance, to the subject, or to the feelings.

Quickness of perception or discernment; penetration of mind; the faculty of nice discrimination. Selden.

ions, by passing under the divided vessel a needle, the ends of which are left exposed externally on the cutaneous surface. Simpson.

Having nice discernment; perceiving or using minute distinctions; penetrating; clever; shrewd; -- opposed to Ant: dull or Ant: stupid; as, an acute observer; acute remarks, or reasoning.

The faculty of nice discernment or perception; acumen; keenness; sharpness; sensitiveness; -- applied to the senses, or the understanding. By acuteness of feeling, we perceive small objects or slight impressions: by acuteness of intellect, we discern nice distinctions. Perhaps, also, he felt his professional acuteness…

hardness; a name given to the diamond and other substance of extreme hardness; but in modern minerology it has no technical signification. It is now a rhetorical or poetical name for the embodiment of impenetrable hardness. Opposed the rocky orb Of tenfold adamant, his ample shield. Milton.

A genus of ferns (Ophioglossum), whose seeds are produced on a spike resembling a serpent's tongue.

A governor of a province; a commander. Prescott.