The Collaborative International Dictionary of English v.0.48:
Reconnaissance \Re*con"nais*sance\, Reconnoissance
\Re*con"nois*sance\(r?-k?n"n?s-s?ns), n. [F. See
The act of reconnoitering; preliminary examination or survey.
(a) (Geol.) An examination or survey of a region in reference
to its general geological character.
(b) (Engin.) An examination of a region as to its general
natural features, preparatory to a more particular survey
for the purposes of triangulation, or of determining the
location of a public work.
(c) (Mil.) An examination of a territory, or of an enemy's
position, for the purpose of obtaining information
necessary for directing military operations; a
Reconnoissance in force (Mil.), a demonstration or attack
by a large force of troops for the purpose of discovering
the position and strength of an enemy.
[1913 Webster] Reconnoiter