Noah Webster's New International Dictionary of the English Language

1. (v. i.) To make a low, hoarse noise in the throat, as a frog, a raven, or a crow; hence, to make any hoarse, dismal sound.

2. (v. i.) To complain; especially, to grumble; to forebode evil; to utter complaints or forebodings habitually.

3. (v. t.) To utter in a low, hoarse voice; to announce by croaking; to forebode; as, to croak disaster.

4. (n.) The coarse, harsh sound uttered by a frog or a raven, or a like sound.