file name extension

Thesaurus

Noun

1.

file name extension - a string of characters beginning with a period and followed by one or more letters; the optional second part of a PC computer filename; "most applications provide extensions for the files they create"; "most BASIC files use the filename extension .BAS" filename extension, extension computer file name, computer filename, file name, filename - (computer science) the name given to a computer file in order to distinguish it from other files; may contain an extension that indicates the type of file string - a linear sequence of symbols (characters or words or phrases)