noun
tacit agreement; unspoken understanding
Refers to an implicit agreement or understanding between parties without explicit verbal confirmation. The gloss 'default' is a less common, context-specific rendering.
二人の間には、その問題について黙約があった。
There was a tacit agreement between the two of them on that matter.
黙約のうちに、彼がリーダー役を引き受けることになった。
By unspoken understanding, he ended up taking on the role of leader.