Definition of "thunderhead" [thun•der•head]

• The swollen upper portion of a thundercloud, usually associated with the development of a thunderstorm. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "At his feet swept the broad and noble river, reflecting on its surface the snowy masses of "thunderhead" clouds, around which the lightning still played, and which, transfigured and glorified in the light of the setting sun, seemed to the poetic imagination of the young man like the City of God descending out of heaven, with its streets of gold and foundations of precious stones, while the rainbow that spanned the heavens seemed like the rainbow of the Apocalypse round about the throne of God."
• "I looked back to shore and saw we now had this enormous slate-gray thunderhead approaching us."
• "I tracked a deer last week shot with a 100gn thunderhead."