Constrictor \Con*strict"or\, n.

1. That which constricts, draws together, or contracts.

2. (Anat.) A muscle which contracts or closes an orifice, or which compresses an organ; a sphincter.

3. (Zo["o]l.) A serpent that kills its prey by inclosing and crushing it with its folds; as, the boa constrictor.

Source: Webster's Revised Unabridged Dictionary (1913)