This is a tough one. I can assure you that you will not master the usage of the word ormai just by reading the dictionary, which will unhelpfully give you "equivalents" such as "now" or "by now" ("by then" if speaking of the past) and even "almost."
The word ormai expresses a view or a mood associated with an occurrence or action with reference to time- more specifically, the end or near-end of a lapse of time. There is usually the idea that the passage of time has not been correctly perceived; thus, the mood is often, but not always, one of resignation or a sobering acknowledgement of relative lateness. Let's take a look at some examples:
Ormai i bambini sono grandi.
The children are grown now. (They're not kids anymore, soon they'll be leaving home, we can't tell them what to do, etc.)
Ormai ho capito che tipo e'.
I've finally understood what kind of man he is. (Not a very good kind, I should have caught on sooner)
Sono le undici ormai.
It's eleven o'clock (now). (It's getting late, hadn't really noticed, time to go home/turn in/wind down)
Quell'attrice ha ormai cinquant'anni.
That actress is (now) fifty. (She's getting up there, not as good-looking, harder to find good roles, she'd better face up to it)
You'll be pleased to know ormai is not always so wistful or mildly depressing.
Siamo arrivati ormai.
We're practically there. (Said for example to whining children on a trip)
Ormai e' fatta.
It's done now. (It's finally finished; may also suggest irreversibility, which again is mildly depressing)
Ormai sara' arrivato a casa.
He should be home by now.
In its resignation mood it can even be used alone.
-Perche' non ci provi un'altra volta?
-Why don't you try again?
-No/It's useless/It's too late