Here's what rhymes with sternocleidomastoid.

Consider these alternatives

trapezius / ideas transversus / service levator / later orbicularis / orbiculoris hallucis / uses pollicis / wishes pronator / later brachialis / radialis serratus / status interventricular / ventricular radialis / brachioradialis obturator / later sphenopalatine / line interosseous / interosseus