semisulcus

A slight groove on the edge of a bone or other structure, which, uniting with a similar groove on the corresponding adjoining structure, forms a complete sulcus.

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semi·sul·cus (sem″e-sulґkəs) [semi- + sulcus] a slight channel on the edge of a bone or other structure, which unites with a similar channel on a corresponding adjoining structure to form a complete sulcus.