Focus  —n. (pl. Focuses or foci) 1 a point at which rays or waves meet after reflection or refraction. B point from which rays etc. Appear to proceed. 2 a point at which an object must be situated for a lens or mirror to give a well-defined image. B adjustment of the eye or a lens to give a clear image. C state of clear definition (out of focus). 3 = *focal point 2. —v. (-s- or -ss-) 1 bring into focus. 2 adjust the focus of (a lens or eye). 3 concentrate or be concentrated on. 4 converge or make converge to a focus. [latin, = hearth]