Plain English Meaning
A tiny unit of power. One thousand milliwatts make up one watt.
Full Definition
A unit of electrical power equal to one one-thousandth of a watt (0.001 W). Used to express very small amounts of power, such as the signal strength of weather balloon transmitters and other low-power radio equipment.
Context Anchor
Seen in upper-air observation discussions when describing small electronic instruments carried by weather balloons or other weather-sensing equipment.
Derivation
From the Latin 'mille' meaning 'thousand', combined with 'watt' (the standard unit of power, named after Scottish engineer James Watt). The prefix 'milli-' always signals one-thousandth of the base unit.
Why Pilots Care
Weather balloon radiosondes transmit on very low power -- often just a few hundred milliwatts -- yet their feeds the upper-air and pilots rely on for .