blunder upon, bump into, chance upon, come across, come among, come down on, come on, come up against, come upon, confront, descend upon, discover serendipitously, drop on, encounter, fall across, fall among, fall foul of, fall in with, fall on, fall upon, happen upon, hit upon, light upon, meet, meet head-on, meet up with, meet with, pitch upon, run across, run into, run smack into, run up against, run upon, settle on, strike upon, stumble on, stumble upon, tumble on