handshake

Short definition from Wiktionary

Noun

1. 1
   The grasping of hands by two people when greeting, leave-taking, or making an agreement.
2. 2
   An exchange of signals between two devices when communications begin in order to ensure synchronization.

Verb

1. 1
   To perform a handshake; to shake hands.
2. 2
   To perform a handshake with another device.