[very common; always pronounced as if capitalized. Orig. fr. the 1930 Sellar & Yeatman parody of British history 1066 And All That, but well-established among hackers in the U.S. as well.]
1. Self-evidently wonderful to anyone in a position to notice:
A language that manages dynamic memory automatically for you is a
Good Thing.
2. Something that can't possibly have any ill side-effects and may
save considerable grief later: Removing the self-modifying code from
that shared library would be a Good Thing.
3. When said of software tools or libraries, as in YACC is a
Good Thing
, specifically connotes that the thing has drastically
reduced a programmer's work load. Oppose
Bad Thing.