Frost signal

Frost´ sig`nal

1.(Meteor.) A signal consisting of a white flag with a black center, used by the United States Weather Bureau to indicate that a local frost is expected. It is used only in Florida and along the coasts of the Pacific and the Gulf Mexico.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
By using the passage as an introduction to the entire volume of poems in In the Clearing, Frost signaled his belief that the penetration of God's spirit into matter encompasses the whole history and development of European and Western civilization.