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).
I paid back the debt all at once.
I paid six months' rent in one lump sum.
Standard kanji-kana mixed spelling; 耳 is used for its meaning, and the rest is in kana.
Alternate spelling using the kanji 揃 for 'to align'; less common but still encountered.
耳 refers here to the projecting edges of coins or similar objects. 耳を揃える, literally “align the edges,” came to mean assembling the full amount of money neatly and without deficiency.