A secondary heading, especially one printed above another(noun)
A memorable slogan attached to a commercial brand(noun)
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Use "strapline" in a sentence
"The strapline is shorter, and elements of the image and shading are sharpened up."
"The City Paper story appears to accuse the city of singling out bloggers – if you only read the strapline, that is."
"The viewer's complaint was upheld, but the ASA's challenge was not because it accepted Mars 'argument that the strapline is a trademark that has been in use since 2005 and therefore its use in advertising could not currently be in breach of the regulation."