ˈflīsnə(r)- noun
Usage: usually capitalized F
Etymology: after Eduard Fleissner von Wostrowitz, Austrian cryptographer
: a square grille designed to be reconstructed from a key word and used for cryptographic transposition without cover text and to be rotated 90 degrees on the paper whenever the spaces are exhausted so that a solid block of transposed ciphertext is produced after four successive turns or sometimes when reversal of the grille is provided for after eight turns