[ar.ris] n, pl arris or ar.ris.es [prob. modif. of MF areste, lit., fishbone, fr. LL arista--more at arete] (1677): the sharp edge or salient angle formed by the meeting of two surfaces esp. in moldings
ARRIS
Meaning of ARRIS in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012