The pilot episode (2007) of The Big Bang Theory gives a good definition of the practice of astrology:
Leonard: So, tell us about you.
Penny: Um, me? Okay – I’m a Sagittarius, which probably tells you way more than you need to know.
Sheldon: Yes – it tells us that you participate in the mass cultural delusion that the sun’s apparent position relative to arbitrarily defined constellations at the time of your birth somehow affects your personality.
Penny: [stares at Sheldon in utter confusion] Participate in the what?
Leonard: [trying to keep things polite] I think what Sheldon is trying to say is that Sagittarius wouldn’t have been our first guess.
Penny: Oh, yeah – lot of people think I’m a water sign.