expression
all at once; in one lump sum
Colloquial expression, typically used for paying money in full at one time rather than in installments. Often appears with verbs like 払う (pay).
借金を耳そろえて返した。
I paid back the debt all at once.
家賃を半年分、耳そろえて払った。
I paid six months' rent in one lump sum.
一括 is a more formal term for 'lump sum' or 'all together', used in business and official contexts, while 耳そろえて is colloquial and often limited to payment situations.
まとめて means 'collectively' or 'in one batch' and is more general; 耳そろえて specifically emphasizes paying the full amount at once, often with a nuance of settling a debt.
The phrase literally means 'aligning ears', but the exact origin is uncertain. It may derive from the image of aligning animals by their ears when gathering them together, metaphorically extended to gathering money into one sum.