Generally, itīs synonymous of minimal value.

In telecommunication, the term threshold has the following meanings:

1. The minimum value of a signal that can be detected by the system or sensor under consideration.

2. A value used to denote predetermined levels, such as those pertaining to volume of message storage, i.e., in-transit storage or queue storage, used in a message switching center.

3. The minimum value of the parameter used to activate a device.

4. The minimum value a stimulus may have to create a desired effect.

Source: from Federal Standard 1037C and from MIL-STD-188