As is obvious from its name, anti-bubble is the opposite of bubble. An anti-bubble is a droplet of liquid surrounded by a thin film of gas, while a gas bubble is a sphere of gas surrounded by a liquid. Anti-bubbles are formed when liquid drops or flows turbulently into the same or another liquid. This video explains the amazing physics behind anti-bubbles.
Top gif image created from the video.
[Source: Physics Girl via YouTube]