v. Math. [f. L. con- together + vānēscĕre to vanish.] To disappear by the running together of two summits: said of the edge of a polyhedron.
1851. E. P. Kirkman, in Phil. Trans., CXLVII. 187. If AB convanesces by the union of its summits, P becomes P′, losing the faces A and B.
