To be of the right size and shape for someone or something. The dress fits her perfectly.
To be suitable or appropriate for someone or something. This job fits him well because of his skills.
To adjust or make something suitable for a particular purpose or situation. They need to fit the equipment to the new specifications.
To insert or fix something into a particular place or position. He fitted the new lock onto the door.
To equip or supply (someone or something) with a particular item or items. They fitted the house with new smoke detectors.