1. To fasten, attach, or hold tightly on (to someone or something). Be careful around that animal—if it latches on with its teeth, it won't let go. My son latched on to my arm when the movie became too intense for her.

2. To fasten or attach something to someone or something. In this usage, a noun or pronoun can be used between "latch" and "on." I just need to latch the trailer on the truck, and we'll be ready to go. Once you latch the antenna on, we should be able to communicate to the control tower.

3. To begin to comprehend, understand, or make sense of something. Once he latched on to the instructions in the manual, he was able to complete the repair. He's explained it twice already, but I'm still having trouble latching on.

4. To become fixated on or accepting of some idea, notion, or belief. I don't know why he's latched on to this idea of moving to Canada, but he seems dead set on it now. I'll try to get the rest of the board members to latch on if you can show some data to back up your plan.

5. To become closely involved or associated with a person or group. I was friendly with one guy during our orientation for the graduate program, but then he latched on and started following me around campus for the rest of the day. Tom's really latched on to the local rowing club.