Related Clues:

• Change color, maybe
• Trace criminal for answer
• Respond to a provocation
• Change in response to a stimulus
• Blink, say
• Respond when crate broken
• Giggle or gasp
• Duck, e.g
• Respond to soldiers and behave
• Gush violently
• Emulate an active volcano
• Respond to a 13
• Do a spit take, perhaps
• Do a spit-take, say
• Blink, perhaps