cleido-mastoidadj.n.

/klʌɪdəʊˈmastɔɪd/Etymology: < Greek κλείς, κλειδ- key, clavicle + mastoid adj. and n.
Anatomy.
1849–52 IV. i. 725/1 That part..becomes confounded with the deltoid and with the cleido-mastoid.
1882 in
This entry has not yet been fully updated (first published 1889; most recently modified version published online June 2022).