laugh

As a noun laugh

is an expression of mirth particular to the human species; the sound heard in laughing; laughter.

As a verb laugh

is 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.

As an initialism PMSL is

pissing myself laughing; used to indicate great amusement.

As nouns the difference between laugh and hypergelast

is that laugh is an expression of mirth particular to the human species; the sound heard in laughing; laughter while hypergelast is someone who laughs excessively.

As a verb laugh

is (label) 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.