fricative

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

• noun A consonant, such as f or s in English, produced by the forcing of breath through a constricted passage.
• adjective Of, relating to, or being a fricative consonant.

from The Century Dictionary.

• Characterized by friction: said of those alphabetic sounds in which the conspicuous element is a rustling of the breath through a partly opened position of the organs, as s and sh, z and zh, f and v, th and Ŧh, and so on. They are sometimes divided into subclasses, as sibilants, like s and sh, and spirants, like f and verb
• Sounded by friction, as certain musical instruments. See instrument, 3 .
• noun A fricative consonant. See I., 1.

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

• adjective (Phon.) Produced by the friction or rustling of the breath, intonated or unintonated, through a narrow opening between two of the mouth organs; uttered through a close approach, but not with a complete closure, of the organs of articulation, and hence capable of being continued or prolonged; -- said of certain consonantal sounds, as f, v, s, z, etc.

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

• noun phonetics Any of several sounds produced by air flowing through a constriction in the oral cavity and typically producing a sibilant, hissing, or buzzing quality; a fricative consonant. English /f/ and /s/ are fricatives.
• adjective phonetics produced by air flowing through a restriction in the oral cavity.

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

• noun a continuant consonant produced by breath moving against a narrowing of the vocal tract
• adjective of speech sounds produced by forcing air through a constricted passage (as `f', `s', `z', or `th' in both `thin' and `then')