An onomatopoeia for a short snapping/clapping/crackling sound (e.g., a book snapping shut, a clap, a small crack).
彼は本をパチっと閉じて話をやめた。
He snapped the book shut with a 'pachi' and stopped talking.
暗闇の中で何かがパチパチと音を立てている。
Something is crackling/popping in the dark.
拍手が起きると、パチパチと鳴り響いた。
When people started clapping, it sounded 'pachi pachi' all around.
Slang abbreviation for pachinko (the gambling arcade/game); used colloquially to refer to going to or playing pachinko.
週末は友達とパチに行って時間をつぶした。
I killed time at the pachinko parlor with friends over the weekend.
彼はパチにハマって借金が増えてしまった。
He got hooked on pachinko and his debts increased.