• noun:   a dome-shaped covering made of transparent glass or plastic
• noun:   an impracticable and illusory idea

  Example: "He didn't want to burst the newcomer's bubble"

• noun:   a hollow globule of gas (e.g., air or carbon dioxide)
• noun:   a speculative scheme that depends on unstable factors that the planner cannot control

  Example: "A real estate bubble"

• verb:   form, produce, or emit bubbles
• verb:   expel gas from the stomach
• verb:   flow in an irregular current with a bubbling noise

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