Real Dictionary

spline in American English
a long, flat, pliable strip, as of wood or metal, esp. one used in drawing curves
to fit with a spline
noun: a long, narrow, thin strip of wood, metal, etc.; slat

spline in British English
noun: any one of a series of narrow keys ( external splines) formed longitudinally around the circumference of a shaft that fit into corresponding grooves ( internal splines) in a mating part: used to prevent movement between two parts, esp in transmitting torq
verb: to provide (a shaft, part, etc) with splines

spline in Mechanical Engineering
noun: Splines are narrow ridges around the circumference of a shaft (external splines) or the grooves that these ridges fit into (internal splines). They are used to prevent rotational movement between two parts.