Related Clues:

• Open wide
• Gape
• Be wide open
• [bo-o-o-ring!]
• Respond to a bore
• Demonstrate boredom
• Hint to an unexciting speaker
• Sign from the bored
• Sign of boredom
• [bor-r-ring!]
• Show sleepiness
• [That is, like, so last week]
• [Been there, done that]
• React with ennui
• Occurrence at many a lecture