Zamzama is a Persian word meaning "Thunder," or "Roar", but can also mean "murmur" or "whisper to oneself". As with many Arabic and Persian words, it has been taken into Urdu and is now considered indigenous to that language. The meaning is: addition of notes. Zamzama is a type of Alankara or Alankar (Sanskrit: decorating with ornaments, ornamentation of sound (sabda-alankara)) and part of the ornamentic in Indian Classical music, mainly for Raga performances - instrumental same as vocalistic.
Like a khatka, another type of Alankara, Zamzama is a cluster of notes, which is used by the musician (vocalist or instrumentalist) to embellish the landing note. The difference to a khatka is, that the notes (swara) in a Zamzama are rendered in progressive combinations and permutations. For the listener it sounds like a complex taan pattern with sharp gamaks.
Zamzamas are an integral part of tappa singing (a Punjabi style of Indian classical vocals) and best applied herefore. In Khayal renditions - a vocal style of North Indian Classics (Hindustani) it must be applied with great caution by the vocalist.