What does "$<\!\!<\!\!<$" mean?

Question

What does the symbol $<\!\!<\!\!<$ mean? It is normally followed by a number. An example:

It would be appreciated if you could explain it in fairly basic terms.

Answer 1

$$x<\!\!<\!\!<k$$ normally means cyclic rotation of a bit string $x$ to the left by $k$ bits.