noun
total mismatch; ill-suited; square peg in a round hole
A yojijukugo literally meaning 'square base, round lid', used to describe things that are fundamentally incompatible or mismatched. Often used in formal or written contexts.
彼の提案と我々の計画は方底円蓋だ。
His proposal and our plan are a total mismatch.
この契約は方底円蓋で、双方にとって利益がない。
This contract is ill-suited and benefits neither party.
A yojijukugo composed of 方 (square), 底 (base), 円 (round), and 蓋 (lid). The literal image of a square base with a round lid that cannot close properly is used metaphorically to express a fundamental mismatch.