Constrictor

Noun

1. That which constricts or tightens: A muscle whose contraction narrows a vessel or passage or compresses an organ.
2. A muscle whose contraction narrows a vessel or passage or compresses an organ.
3. Ellipsis of pharyngeal constrictor (“each of the muscles which constrict the pharynx”).
4. Ellipsis of boa constrictor, either the species Boa constrictor or a similar snake that kills by constriction.