An Etymological Dictionary of Astronomy and Astrophysics

1. General: Pointed end. A point of transition. → polar cusp.
   

2. Either point of a → crescent moon.
   

3. A steep power-law representing the number density of stars in the central region of a galaxy. Cusps are characteristic of low-mass ellipticals. They are thought to result from the gravitational attraction of a central → supermassive black hole.
   

4. A peaked concentration of dark matter in the center of galaxies, as predicted by the → cold dark matter (CDM) model of galaxy formation. See also → cusp problem.
   

5. Math: A tooth-like meeting of two branches of a curve, with sudden change of direction.

Etymology (EN): L. cuspis “point, spear, pointed end.”

Etymology (PE): Tizé, noun from tiz “sharp, pointed,” from Mid.Pers. tēz, tēž, tigr “sharp,” O.Pers. tigra- “pointed,” Av. taēža-, tighra- “pointed,” Skt. taējas- “the sharp edge (of a knife), piercing (flame)”, from tij- “to be sharp, to pierce,” Gk. stizein “to prick, puncture,” stigma “mark made by a pointed instrument,” L. instigare “to goad,” P.Gmc. *stik- “to pierce, prick, be sharp,” O.H.G. stehhan, Ger. stechen “to prick,” O.E. stician “to pierce, stab,” E. stick “to pierce;” PIE *st(e)ig- “to stick; pointed”.