What is "memorising"

Usage examples of "memorising".

He wandered around with seeming aimlessness, memorising all geographical features that might prove useful to recall later on.

Then he sat frowning at it with his mouth hanging open, selecting from it, memorising and rejecting simultaneously, the way a Method actor might read his lines: I'll say this but say it differently, I won't say that at all, I'll do this but my way not his.