attenuate

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

• intransitive verb To make slender, fine, or small.
• intransitive verb To reduce in force, value, amount, or degree; weaken.
• intransitive verb To lessen the density of; rarefy.
• intransitive verb Biology To make (bacteria or viruses) less virulent.
• intransitive verb Electronics To reduce (the amplitude of an electrical signal) with little or no distortion.
• intransitive verb To become thin, weak, or fine.
• adjective Reduced or weakened, as in strength, value, or virulence.
• adjective Botany Gradually tapering to a slender point.

from The Century Dictionary.

• Slender; thin.
• In botany, tapering gradually to a narrow extremity.
• Of thin consistency; dilute; rarefied.
• To make thin or slender; reduce in thickness; wear or draw down: as, an attenuated thread or wire.
• To reduce by comminution or attrition; make small or fine: as, extremely attenuated particles of dust or flour.
• To make thin or rare; reduce in density; increase the fluidity or rarity of.
• To lessen in complexity or intensity; reduce in strength or energy; simplify; weaken: as, the attenuated remedies of the homeopathists.
• Figuratively, to weaken or reduce in force, effect, or value; render meager or jejune; fine down.
• To lessen; diminish: said of number. Howell.
• To become thin, slender, or fine; diminish; lessen.
• In brewing and distilling, to undergo the process of attenuation. See attenuation, 4.

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

• intransitive verb To become thin, slender, or fine; to grow less; to lessen.
• adjective Made thin or slender.
• adjective Made thin or less viscid; rarefied.
• transitive verb To make thin or slender, as by mechanical or chemical action upon inanimate objects, or by the effects of starvation, disease, etc., upon living bodies.
• transitive verb To make thin or less consistent; to render less viscid or dense; to rarefy. Specifically: To subtilize, as the humors of the body, or to break them into finer parts.
• transitive verb To lessen the amount, force, or value of; to make less complex; to weaken.

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

• verb transitive To reduce in size, force, value, amount, or degree.
• verb transitive To make thinner, as by physically reshaping, starving, or decaying.
• verb transitive To weaken.
• verb transitive To rarefy.
• verb transitive, medicine To reduce the virulence of a bacteria or virus.
• verb transitive, electronics To reduce the amplitude of an electrical signal.
• adjective botany, of leaves Gradually tapering into a petiole-like extension toward the base.

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

• verb weaken the consistency of (a chemical substance)
• adjective reduced in strength
• verb become weaker, in strength, value, or magnitude