What does a tilde underneath an inequality mean? I've recently come across an expression of the form
$$\large x \lesssim y$$
What does this expression mean?

One possible interpretation of $x \lesssim y$ is,
$$x < y \ \mbox{ or }\ x \approx y.$$
This is analogous to the way $x \le y$ signifies "$x < y$ or $x = y$."
But from the comments, clearly this is not the only way this symbol might be used.
One would hope that prior to its first use in a publication, the same publication would define the symbol.
