It specifically implies an encounter with someone while traveling in the opposite direction.
Here are some examples:
* "Nakasalubong ko siya sa daan." (I met him/her on the road.)
* "Nakasalubong ko ang aking mga kaibigan sa mall." (I encountered my friends at the mall.)
The word "nakasalubong" comes from the Tagalog verb "salubong," which means "to meet" or "to encounter." The prefix "na-" indicates that the action has already happened.