Meaning:
a loose fitting dress worn by women in the summer

Usage Example:
祖母はこの時期、あっぱっぱを着ていたと懐かしそうに話した。 (In a nostalgic tone grandmother said she used to wear an appappa during this season.)

Notes:
Started to be used during the Taishō period (1912 – 1926) in the Kansai area (大正から昭和にかけて関西圏で使用されるようになった俗語)