Definition of "open-mouthed"

Againe, what is it that makes men to be open mouthed, in decla∣ring and censuring our faults […] ?

1606, William Perkins, The whole treatise of the cases of conscience […] ‎, page 624

A politician who has been open-mouthed against extravagant expenditure is in no way called upon to object to expenditure which, even if increased, has ceased to be extravagant.

1870, William Rathbone Greg, Political Problems for Our Age and Country, page 185

Men must be found who will not manifest anything but a Christ-like spirit when opposed by talkative, open-mouthed men who put light for darkness and darkness for light.

1894 October 23, E. [Ellen] G. White, “Truth to be Rescued from Error”, in The Advent Review and Sabbath Herald, volume 71, number 42, page 657