Related Clues:

• This one of 21 across may be the last
• Last gasp comes at last and leaves one quite breathless
• 'Unbelievable!' noise
• "Unbelievable!" noise
• Letters of surprise, in text messages
• Sound dumbfounded
• [Oh my God!]
• George Harrison's autobiography
• Exclaim breathlessly
• Text messager's 'Wow!'
• Shorthand for the shocked
• Texter's "No way!"
• Text-speak gasp
• 'Yikes!,' to a texter
• Texter's 'Wow!'