The time it takes for a packet of information to be transmitted and received over the Internet, typically measured in milliseconds. In a VoIP system, a latency higher than 100 milliseconds (ms) causes your caller to experience audio that lags. Higher than 500 milliseconds and the conversation is going to be unintelligible.
Merriam-Webster Online Dictionary
latency (noun)1.
the quality or state of being - latent dormancy
2.
something latent
3.
a stage of psychosexual development following the phallic stage that extends from about the age of five or six to the beginning of puberty and during which sexual urges often appear to lie dormant
4.
- latent period
Latency (Wikipedia)