To be easily accommodated; fit: The puzzle piece fits in here.
2. To belong to a group or to have similarities with members of a group: I never fit in with the popular crowd at school. The kids felt awkward in their new school, but soon they found that they fit in well.
3. To be logically or seamlessly related to something; mesh: My role as supervisor fits in with my authoritative personality.
4. To cause something to be placed or accommodated within specific limits: I don't know if we can fit the paragraph in the space provided. We can fit you in at noon.