Flash Tag 

When using FB check-in and you tag not only the group you are with, but start tagging random people in your friends list causing havoc.

Eddie checking his FB feed: Damm it I got Flash Tagged again! If my wife sees this she'll think I was out again and I'm gonna get cutoff.

Flash Tag by Mikeyl16 May 17, 2011

flashtaging 

Someone who over hashtags their tweets on Twitter to gain more exposure.

most #underrated #britpop band, without question: #supergrass #fuckyou #thingsweneedtochange

"I have to unfollow Steve on Twitter. I am sick of his flashtaging. I can't even get through a message with only 120 characters."

flashtaging by Hashtag Failer September 2, 2011

Flashtagram

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

Flashtagram by ladyluck81 August 12, 2014

Flashtag

To sum up your Twitter post in one word

My Mum is singing campfire hymns #Mumbyah ...I totally flashtagged that one

Flashtag by GoggleboxUK May 12, 2015