Noah Webster's New International Dictionary of the English Language

1. (a.) Not tense, firm, or rigid; loose; slack; as, a lax bandage; a lax standard of discipline; lax fiber.

2. (v. t.) Not strict or stringent; not exact; loose; weak; vague; equivocal.

3. (v. t.) Having a looseness of the bowels; diarrheal.

4. (n.) A looseness; diarrhea.