'Mental arithmetic' definitions:

Definition of 'Mental arithmetic'

From: GCIDE

Mental \Men"tal\, a. [F., fr. L. mentalis, fr. mens, mentis, the mind; akin to E. mind. See Mind.] Of or pertaining to the mind; intellectual; as, mental faculties; mental operations, conditions, or exercise. [1913 Webster]
What a mental power This eye shoots forth! --Shak. [1913 Webster]
Mental alienation, insanity.
Mental arithmetic, the art or practice of solving arithmetical problems by mental processes, unassisted by written figures. [1913 Webster]