Bubble

a hollow globule of gas (e.g., air or carbon dioxide)

a speculative scheme that depends on unstable factors that the planner cannot control

an impracticable and illusory idea

a dome-shaped covering made of transparent glass or plastic

form, produce, or emit bubbles

flow in an irregular current with a bubbling noise

rise in bubbles or as if in bubbles

cause to form bubbles

expel gas from the stomach