spat (n.1)

"petty quarrel," 1804, American English, of unknown origin; perhaps somehow imitative (compare spat "smack, slap," attested from 1823).

spat (n.2)

"short gaiter covering the ankle" (usually only in plural, spats), 1779, shortening of spatterdash "long gaiter to keep trousers or stockings from being spattered with mud" (1680s), from spatter and dash (v.).

spat (n.3)

"spawn of a shellfish," especially "spawn of an oyster," also "a young oyster," 1660s, of unknown origin, perhaps from the past tense of spit (v.1).

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Definitions of spat from WordNet
spat (v.)
come down like raindrops;
Bullets were spatting down on us
spat (v.)
become permanently attached;
mollusks or oysters spat
spat (v.)
strike with a sound like that of falling rain;
Bullets were spatting the leaves
spat (v.)
clap one's hands or shout after performances to indicate approval;
Synonyms: applaud / clap / acclaim
spat (v.)
engage in a brief and petty quarrel;
spat (v.)
oysters spat
spat (v.)
clap one's hands together;
Synonyms: clap
spat (n.)
a quarrel about petty points;
Synonyms: bicker / bickering / tiff / squabble / pettifoggery / fuss
spat (n.)
a cloth covering (a legging) that covers the instep and ankles;
Synonyms: gaiter
spat (n.)
a young oyster or other bivalve;