What is the meaning of бе?

second/third-person singular imperfect/aorist indicative of съм (sǎm)

: alternative form of ба (ba): used as an expression of disbelief, surprise, irritation, or eagerness

: alternative form of бре (bre): used for emphasis after vocative expressions

used for emphasis in enumeration of entries

A particle expressing anger, frustration, or surprise.

without

sans

Particle for forming yes-or-no questions.

The letter б (b), the 2nd letter of the Ukrainian alphabet.

Source: wiktionary.org