Foil in thin strips; ejected into the air as a radar countermeasure WordNet 3.0 & Open English WordNet

Chaff, originally called Window by the British and Düppel by the Second World War era German Luftwaffe, is a radar countermeasure in which aircraft or other targets spread a cloud of small, thin pieces of aluminium, metallized glass fibre or plastic, which either appears as a cluster of primary targets on radar screens or swamps the screen with multiple returns, in order to confuse and distract. Wikipedia

A radar countermeasure for aircraft or other targets Wikipedia Disambiguation

Radar countermeasure Wikidata

Loose material, e.g. small strips of aluminum foil dropped from aircraft, intended to interfere with radar detection. Wiktionary

Loose material dropped from aircraft to interfere with radar. Wiktionary (translation)