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A flash mob that occurs on Instagram, when a group of Instagramers post predetermined images at a set time to amuse and confuse followers, or show support for a particular cause or event.
To make Celeste's birthday that much more special, her friends planned a flashtagram between 12am and 1am on the day of her 21st birthday and posted their fav pics of Celeste with the hashtag #Happy21Celeste
by ladyluck81 August 12, 2014
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