Engrossed in your phone or device while being oblivious to the world
It's the worst when you're walking down a crowded sidewalk and you get stuck behind someone walking slowly because they're thumbling.
by Munirih19 September 15, 2014
The act of typing with only your thumbs on all typing devices, I.e. Computer keyboards and other devices through the learned behavior of texting on smaller devices such as cell phones.
Jason thumbled out his term papers on his computer keyboard to the amazement of his parents. "Mom, where are the bandaids? My thumbs are sore from thumbling!"
by Walter eagle December 16, 2010