roughly; approximately; more or less — indicating an approximate amount or extent.
ざっと人数を数えた。
I roughly counted the number of people.
予算をざっと見積もる。
Roughly estimate the budget.
ざっと読んだだけだ。
I only skimmed it.
cursorily; briefly; quickly — doing something in a quick, superficial way rather than in detail.
書類にざっと目を通した。
I briefly skimmed the documents.
彼はざっと説明して終わった。
He gave a quick, cursory explanation and finished.
出かける前に部屋をざっと掃除した。
I did a quick clean-up of the room before going out.