sibilant vs spirant

sibilant

noun
  • A consonant having a hissing or hushing sound such as the s or sh in sack or shack. 

adj
  • Characterized by a hissing or hushing sound such as the s or sh in sack or shack. 

spirant

How often have the words sibilant and spirant occurred in a corpus of books? (source: Google Ngram Viewer )