What does "brown nose" mean?

Solicit favor obsequiously, toady. For example, Harry was always brown nosing, but it didn't help his grades. This term originated in the military in the late 1930s, where it meant “to curry favor”; it alludes to ass-kissing when the backside being kissed is less than clean. Despite its scatological origin, today this slangy term is not considered particularly vulgar.