Meaning:

Quiet, on a small scale, and not attracting a lot of attention.

If something (an event, etc.) is low-key, it is not intended to be big, look important, or involve a lot of activities.

Example: Sam and Jane want to keep their wedding as low-key as possible. They will invite only a handful of people to their wedding.

He spent a lot of money for the last presidential campaign, but this time his campaign for re-election will be low-key.

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