1. to try to do more than one is able to do or to go beyond what is reasonable or appropriate
2. to reach or extend over or beyond something
3. to defeat oneself by going too far or being too ambitious

Examples

• The company overreached by expanding too quickly into new markets.
• Don’t overreach yourself by taking on too many projects at once.
• The politician overreached and lost public support.
• The tree branches overreach the fence into the neighbor’s yard.
• His ambition caused him to overreach and ultimately fail.
• The new policy overreaches the government’s authority.
• She overreached when she promised results she couldn’t deliver.