Plain English Meaning
A small amount of cloud at that altitude — covering up to a quarter of the sky, but not none.
Full Definition
In a METAR, FEW is a sky cover contraction indicating that clouds cover more than zero but no more than two-eighths (2/8) of the sky at the reported layer. It is reported with a three-digit height in hundreds of feet above the station (e.g., FEW040 means a few clouds at 4,000 feet AGL).
Context Anchor
Seen in METAR reports in the sky condition section, such as FEW030.
Derivation
FEW is the plain English word 'few,' kept as a three-letter contraction so it fits the standardized METAR format. The threshold (1/8 to 2/8 sky cover) is set by international weather reporting standards rather than the everyday sense of the word.