Post date: Nov 10, 2014 7:58:13 PM
According to [1], any type of operation on the signal s(t) that creates new frequency components is referred to as spectral leakage. Sampling and windowing are epitomes of operations that result in spectral leakage, with "the leakage caused by windowing is a relatively localized spreading of frequency components, often a blurring effect, whereas the aliasing caused by sampling is a periodic repetition of the entire blurred spectrum" [1]. However, in general, any time-domain multiplication with s(t) naturally leads to a convolution in the frequency domain, which inherently creates new frequency components.
[1] http://en.wikipedia.org/wiki/Spectral_leakage