Definition: Of a periodic quantity. Having a waveform that is the same as that of a sine function. It is only the shape of the graph that is significant. For example, two e.m.f.s represented by e1 = E1 sin wt and e2 = E2 cos wt would both be described as sinusoidal e.m.f.s, and are both sine waves.
Source: The Penguin Dictionary of Physics. London: Penguin, 2009. Credo Reference. Web. 17 August 2012.