‖n. [ L., fr. niti, p. p. nisus, to strive. ] 1. A striving; an effort; a conatus. [ 1913 Webster ]
A nisus or energizing towards a presented object. Hickok. [ 1913 Webster ]
2. (Physiol.) (a) The periodic procreative desire manifested in the spring by birds, etc. (b) The contraction of the diaphragm and abdominal muscles to evacuate feces or urine. [ Webster 1913 Suppl. ]