In Messenger, "bump" is a feature that allows users to resurface a message at the top of a chat, among the most recent messages. When a user bumps a message, it can help remind people of a previous message. To use the bump feature, a user can long-press on the text or photo they want to bump, then go to the "More" option from the bottom right corner, and then tap on "Bump". Bumped messages will be notified to those in the chat. It is important to note that bumping messages is not currently supported in end-to-end encrypted chats.