Low Float
A stock with few publicly-tradeable shares. Small orders move price dramatically.
Low-float stocks (<10M shares) are day-trader favourites for volatility. Squeezes happen when short interest is high + float is small - forced covering sends price parabolic. Also the easiest to manipulate (pump-and-dump).
Related
Learn to actually use Low Float.
Definitions are the easy part. The free first five modules put this on a real chart and make you do the work. No card required.