Noun
English Wikipedia has an article on:Planck timeWikipedia
Planck time (plural Planck times) (Abbreviated as: tP)
(physics) A natural unit of time, equivalent to the time it takes light to traverse one Planck length; it is the duration of time at which quantum gravity effects are expected to become significant.
Current established physical theories are believed to fail at this time scale, and many physicists expect that the Planck time might be the smallest unit of time that could ever be measured, even in principle. Source: Internet
The ideas of Planck length and Planck time in modern physics place a limit on the measurement of time and space, if not on time and space themselves. Source: Internet