Terrific means extremely good or wonderful. When your teacher says you did a terrific job on your essay, she means it was excellent. When you have a terrific time at your friend's birthday party, you mean it was really fun and enjoyable.

You might describe a terrific thunderstorm (impressively powerful), a terrific book (wonderfully entertaining), or a terrific idea (exceptionally clever). The word suggests more enthusiasm than simply saying something is “good” or “nice.” When something is terrific, it stands out as particularly excellent or impressive.