1. too familiar or informal in behavior, especially in a way that is inappropriate or presumptuous
2. knowing something so well that it has become boring or uninteresting

Examples

• The new employee was overfamiliar with the boss on his first day.
• She found his overfamiliar manner quite off-putting.
• The story had become overfamiliar through countless retellings.
• His overfamiliar jokes no longer amused the audience.
• The waiter’s overfamiliar attitude made the customers uncomfortable.
• After years of teaching the same material, it had become overfamiliar to her.