What does "spirant" mean?

Spirant: A term used differently by different authorities; -- by some as equivalent to fricative, -- that is, as including all the continuous consonants, except the nasals m, n, ng; with the further exception, by others, of the liquids r, l, and the semivowels w, y; by others limited to f, v, th surd and sonant, and the sound of German ch, -- thus excluding the sibilants, as well as the nasals, liquids, and semivowels. See Guide to Pronunciation, §§ 197-208.