A kitchen tool used to press soft foods like boiled potatoes or fruits through a mesh to make a smooth purée or paste.
I use a sieve to turn potatoes into smooth mash.
Standard kanji spelling using ごし as kana for the verb part.
Alternate spelling using the kanji 漉 for 'straining'; less common but still seen.
Compound of 裏ごし (from 裏漉し, 'straining by pressing through from the back') + 器 ('tool, device'). The exact historical derivation is uncertain, but the term describes the action of pushing food through a mesh.