sharp as a tack
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.
Words nearby sharp as a tack
sharm al-sheikh,
sharon,
sharon fruit,
sharonville,
sharp,
sharp as a tack,
sharp practice,
sharp-cut,
sharp-eared,
sharp-edged,
sharp-eyed