Select the INCORRECTLY spelt word.

The incorrectly spelt word in the given options is "Accelarate." The correct spelling is "Accelerate."

Here are the correct spellings and definitions of the words:

• Calibrate: To adjust or measure the accuracy of something.
• Accelerate: To increase in speed or rate.
• Proliferate: To increase rapidly in number or extent.
• Insinuate: To suggest or imply something indirectly or subtly.