A colloquial adverb meaning 'almost' or 'nearly', similar to ほぼ but often used for emphasis in conversation.
作業はほぼほぼ終わった。
The work is almost finished.
彼の話はほぼほぼ本当だと思う。
I think what he says is mostly true.
「ほぼ」と同じ意味で、日常会話では「ほぼほぼ」もよく使われる。
In everyday conversation, 'ほぼほぼ' is often used with the same meaning as 'ほぼ'.