The phrase "come across" can be used in a number of ways, from meeting someone unexpectedly to discovering something unexpected. There are a number of other ways to express the same concept, such as "encounter," "stumble upon," "find," "chance upon," "unearth," "happen upon," and "discover." Each of these alternatives can add a slightly different nuance to the meaning of the phrase, with "find" implying that the discovery was intentional and "stumble upon" connoting a more accidental encounter. No matter which phrase you choose, each provides a way to describe the experience of coming across something or someone in an unexpected way.