んばかりにAs if, As if it were about to, About to

Like とばかりに, んばかりに is a construction that is often used to show that something is being done 'as if it were (A)', or 'seeming that it will (A)'. It is thought to be a combination of ん, an abbreviation of む, the classical auxiliary verb used to show intent or strong will in the same way as う and よう, and the adverbial particle ばかり, exhibiting that something is 'basically exactly as described'. As a result, んばかり simply indicates the volitional form of (A) as appearing to be about to happen.

んばかりに will appear linked to the indeterminate form of verbs (ない stem), and then followed by a statement that is being modified by the に. If んばかり will modify a noun instead, の will replace に.

Caution

When attached to the indeterminate form of verbs, there is some contention among linguists whether ん is an abbreviation of む, the classical way of expressing う or よう, or whether it is an abbreviation of ぬ, the classical way of expressing ない. Due to being unable to accurately determine what the actual origin is, it would be advisable to choose whichever variation helps to remember the nuance of the grammar point on a case-by-case basis.