This is the 9061st most frequent Russian word.
рубон
The word "рубон" does not appear to have a clear definition in standard Russian; it may be a misspelling, colloquialism, or regional term.
In this sentence, 'рубанул' (past form of рубануть) is used metaphorically to mean 'chopped' or 'cut forcefully and quickly.'
Он рубанул кусок дерева топором.
He chopped a piece of wood with an axe.
Here, 'рубанула' conveys the sense of expressing something too directly or bluntly by analogy to 'cutting' with speech.
Она рубонула правду прямо в глаза.
She bluntly told the truth directly.
The term 'рубонуло' is employed figuratively to describe an emotional impact, likened to being cut severely.