sharp as a tack

Idioms  

1. Also, sharp as a razor. Mentally acute. For example, She's very witty—she's sharp as a tack. These similes are also used literally to mean “having a keen cutting edge” and have largely replaced the earlier sharp as a needle or thorn. The first dates from about 1900, the variant from the mid-1800s.

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Example Sentences

Irish broadcaster RTÉ described Callard's character as "quirky, unpredictable and sharp as a tack, she carries just enough edge to keep Carrigstown on its toes".

From BBC • Jan. 14, 2026

Whittle said Rutan had been courageous in his final hours at the hospital — sharp as a tack, calm and joking with them about what might come next after death.

From Seattle Times • May 4, 2024

“There are huge individual differences in how people age. Some are sharp as a tack at 90 or 100, some have cognitive impairment in their 50’s,” Aldwin said.

From Slate • Feb. 18, 2023

It didn’t take long to notice the upperclassmen dressed sharp as a tack every day.

From Washington Post • Mar. 20, 2022

He was parked in his pearl-gray Cadillac, sharp as a tack, “cooling it.”

From "The Autobiography of Malcolm X" by Alex Malcolm X;Hailey

Related Words

• able
• active
• deft
• effective
• keen
• ready
• sharp
• vigorous
• wise