light a fire under (someone)
phrase
US, informal
: to cause (someone) to move or work more quickly and effectively
I've never seen him work so hard. Someone must have lit a fire under him.
Cite this Entry
“Light a fire under (someone).” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/light%20a%20fire%20under%20%28someone%29. Accessed 11 Mar. 2026.
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Merriam-Webster unabridged
