From the M-W audio FAQ page:
How can I hear the pronunciation of a word?
The word must be in boldface and followed by a red audio icon: . Click on the audio icon. A pop-up window will open, and in most cases the audio pronunciation will play automatically. Click on the “hear it again” link in the pop-up window to replay the pronunciation. When you are done, close the pop-up window.
Main Entry: 1link [color=red][Red audio icon][/color]
Etymology: Middle English, of Scandinavian origin; akin to Old Norse hlekkr chain; akin to Old English hlanc lank