Dictionary.net

• A slope or sloping toward the front; as, the plongee of a parapet; the plongee of a shell in its course.

2010 - New Age Dictionary Database
By Oddity Software

• A slope or sloping toward the front; as, the plongee of a parapet; the plongee of a shell in its course.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.