Loosely used to mean "in accordance with all the relevaNT rules", especially in connection with some set of constraiNTs defined by software. "The older =+ alternate for += is no longer legal syNTax in ANSI C." "This parser processes each line of legal input the momeNT it sees the trailing linefeed." Hackers often model their work as a sort of game played with the environmeNT in which the objective is to maneuver through the thicket of "natural laws" to achieve a desired objective. Their use of "legal" is flavoured as much by this game-playing sense as by the more conveNTional one having to do with courts and lawyers. Compare language lawyer, legalese. [Jargon File]