Laugh \Laugh\, v. i. [imp. & p. p. Laughed; p. pr. & vb. n. Laughing.]

[OE. laughen, laghen, lauhen, AS. hlehhan, hlihhan, hlyhhan, hliehhan; akin to OS. hlahan, D. & G. lachen, OHG. hlahhan, lahhan, lahh?n, Icel. hl[ae]ja. Dan. lee, Sw. le, Goth. hlahjan; perh. of imitative origin.]

1. To show mirth, satisfaction, or derision, by peculiar movement of the muscles of the face, particularly of the mouth, causing a lighting up of the face and eyes, and usually accompanied by the emission of explosive or chuckling sounds from the chest and throat; to indulge in laughter.

Queen Hecuba laughed that her eyes ran o'er. --Shak.

He laugheth that winneth. --Heywood's Prov.

2. Fig.: To be or appear gay, cheerful, pleasant, mirthful, lively, or brilliant; to sparkle; to sport.

Then laughs the childish year, with flowerets crowned. --Dryden.

In Folly's cup still laughs the bubble Joy. --Pope.

To laugh at, to make an object of laughter or ridicule; to make fun of; to deride.

No wit to flatter left of all his store, No fool to laugh at, which he valued more. --Pope.

To laugh in the sleeve

Source: Webster's Revised Unabridged Dictionary (1913)
 

Laughing \Laugh"ing\, a. & n. from Laugh, v. i.

Laughing falcon (Zo["o]l.), a South American hawk (Herpetotheres cachinnans); -- so called from its notes, which resemble a shrill laughing.

Laughing gas (Chem.), hyponitrous oxide, or protoxide of nitrogen

Source: Webster's Revised Unabridged Dictionary (1913)