LILT
From The Aquarium Wiki
LILT - Lower Incipient Lethal Temperature
The lower limit of an animals environmental temperature that can be tolerated before dying.
Kept at the wrong temperatures, fish will become stressed and can get ill or die. If the temperature is too close to the LILT the fish suffer from hypothermia.
In many cases the LILT and UILT change as your fish mature, which is why fry and young fish are much more sensitive to changes.
- See also UILT