also: ぴしゃっぴしゃっ
adverb
Describes the sound of a flat object repeatedly striking a surface, such as a hand, slipper, or wet cloth. Often used for spanking or slapping sounds.
母親が子供のお尻をぴしゃぴしゃ叩いた。
The mother spanked the child's bottom with repeated slaps.
濡れたタオルを床にぴしゃぴしゃ打ちつける。
He slaps the wet towel against the floor repeatedly.
adverb
Describes the sound of liquid splashing repeatedly, such as waves, rain, or someone splashing water.
子供たちが水たまりでぴしゃぴしゃ遊んでいる。
The children are playing in the puddle, splashing around.
雨が窓にぴしゃぴしゃ当たっている。
The rain is splattering against the window.
びしゃびしゃ describes a heavier, wetter splashing or sopping sound, often implying something is drenched, whereas ぴしゃぴしゃ is sharper and drier.
Onomatopoeic word mimicking the sound of repeated slapping or splashing. The geminate variant ぴしゃっぴしゃっ adds emphasis through consonant gemination.