1. Increase by addition to the periphery of material of the same nature as that already present; e.g., the manner of growth of crystals. Syn: accrementition(2).
2. In dentistry, foreign material (usually plaque or calculus) collecting on the surface of a tooth or in a cavity.
3. A growing together.
[L. accretio, fr. ad, to, + crescere, to grow]