Texas-based Global Language Monitor put together a list of the top words and phrases and found that the word was more popular than Obama and H1N1, commonly known as the "swine flu".
Wrapping up the top five words were 'stimulus' and 'vampire', reports the Telegraph.
Founder Paul Payack said: "In a year dominated by world-shaking political events, a pandemic, the after effects of a financial tsunami and the death of a revered pop icon, the word Twitter stands above all the other words.
"Twitter represents a new form of social interaction, where all communication is reduced to 140 characters. Being limited to strict formats did wonders for the sonnet and haiku.
"One wonders where this highly impractical word-limit will lead as the future unfolds."
The top 15 words were:
1. Twitter
2. Obama
3. H1N1
4. Stimulus
5. Vampire
6. 2.0 - as in suffix attached to the next generation
7. Deficit
8. Hadron
9. Healthcare
10.Transparency
11.Outrage
12.Bonus
13.Unemployed
14.Foreclosure
15.Cartel