A multi-outlet extension device, often with a switch, used to plug in several appliances from one wall socket. Wasei-eigo; not called 'table tap' in English.
wasei-eigo (Japanese-coined English), from table tap
I connected the computer and printer to a power strip.
テーブルタップのスイッチを切ってからプラグを抜いてください。
Please turn off the power strip's switch before unplugging it.