This is the 6427th most frequent Polish word.
całus
Kiss.
The word 'całusa' is used here in the accusative case to signify a direct object—a kiss being given.
Ona dała mi całusa na dobranoc.
She gave me a kiss goodnight.
The word 'całus' is used as a nominative subject in the sentence, indicating the kiss as the performer of the action of mood improvement.
Całus od babci zawsze poprawiał mi nastrój.
A kiss from grandma always improved my mood.
The plural form 'całusy' is used as the nominative subject to describe kisses in general as strengthening family bonds.