This is the 4990th most frequent Russian word.
лбу
The word "лбу" is the dative case of "лоб" (forehead) in Russian, meaning "to/for the forehead."
The word 'лбом' (forehead) is used in the instrumental case as it indicates the tool or means by which the action occurred.
Он ударился лбом о стол.
He hit his forehead on the table.
The word 'лбу' (forehead) is in dative case, indicating the indirect object of the verb (to the forehead).
Капли пота стекали лбу.
Drops of sweat were running down his forehead.
Here, 'лбу' (forehead) is in the dative case, signifying the object towards which the action is directed.