1. to bump into someone: to meet someone by chance
I bumped into Greg at the store.
She bumped into her ex-friend at the concert.
2. to be back in town: to return to town after being gone for a period of time
Mark is back in town.
Tina was in Europe for 3 months, but she has been back in town for a couple days.
3. to keep in touch with someone: to regularly contact or communicate with someone
She moved to New York 2 years ago, but we still keep in touch with each other.
I don't keep in touch with my friends from high school.