dwindle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To become gradually less until little remains. synonym: decrease.
• intransitive verb To cause to dwindle.

from The Century Dictionary.

• To diminish; become less; shrink; waste or consume away: with by or from before the cause, and to, in, or into before the effect or result: as, the body dwindles by pining or consumption; an estate dwindles from waste; an object dwindles in size as it recedes from view; from its constant exposure, the regiment dwindled to a skeleton.
• To degenerate; sink; fall away in quality.
• Synonyms Diminish, etc. (see decrease); attenuate, become attenuated, decline, fall off, fall away.
• noun Gradual decline or decrease; a wasting away; degeneracy; decline.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To make less; to bring low.
• transitive verb rare To break; to disperse.
• intransitive verb To diminish; to become less; to shrink; to waste or consume away; to become degenerate; to fall away.
• noun rare The process of dwindling; dwindlement; decline; degeneracy.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb intransitive To decrease, shrink, diminish, reduce in size.
• verb intransitive, figuratively To fall away in quality; degenerate, sink.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb become smaller or lose substance