[to.rus] n, pl to.ri [NL, fr. L, protuberance, bulge, torus molding] (1563) 1: a large molding of convex profile commonly occurring as the lowest molding in the base of a column--see base illustration
2: the thickening of a membrane closing a wood-cell pit (as of gymnosperm tracheids) having the secondary cell wall arched over the pit cavity
3: a doughnut-shaped surface generated by a circle rotated about an axis in its plane that does not intersect the circle; broadly: toroid
4: a smooth rounded anatomical protuberance (as a bony ridge on the skull)