1.
If you ~ something or someone, you find them or meet them by chance.
I came across a group of children playing.
= encounter
PHRASAL VERB: V P n
2.
If someone or what they are saying comes across in a particular way, they make that impression on people who meet them or are listening to them.
When sober he can ~ as an extremely pleasant and charming young man...
He came across very, very well.
= come over
PHRASAL VERB: V P as n, V P adv