Descriptions of and documents about the Enigma machine refer to a number of terms. This can be confusing, especially when both English and German terms are used. Here is a list I put together of some of the most common terms, and a brief definition of each of them.
BP - Bletchley Park.
Begleitbuch - A record book that accompanied each Enigma unit.
Bomba - A machine designed by the Polish Cipher Bureau to break Enigma ciphers.
Bombe - An electro-mechanical device developed at Bletchley Park by Alan Turing and others to break Enigma ciphers.
Cipher text - the encrypted form of a message.
Clear text - The original, unencrypted, text of a message.
Crib - A section of plain text thought to correspond to the ciphertext.
ETW - Entrittswalze.
Entrittwalze - Entry stator.
Entry stator - stationary entry wheel.
Greek wheel - The fourth rotor of the M4, which could be one of two identified with the Greek letters Beta and Gamma. Also known as Griechenwalze (Greek wheel) or Zusatswalze (additional wheel).
Griechenwalze - See Greek wheel.
Ground Setting - Rotor start position.
Grundstellung - German for "ground setting".
Kennegruppe - Message discriminant (plural Kenngruppen). Groups to identify the key to the receiver. Part of a key sheet.
Lampboard - The Enigma board containing the 26 alphabetic lamps.
Letter blocks - Grouping of an encrypted message in letters, usually 4 or 5 characters per block.
M3 - German Navy version of the Enigma.
M4 - Four rotor version of the Enigma used by the German Navy for U-boat traffic.
Plain text - See clear text.
Plugboard - The front panel board with 26 plugs which could be jumpered by 10 cables.
Reflector - Non-rotating wheel which returned connections back into the rotors.
Reflector Wheel - Reflector.
Reversing drum - See Reflector.
Ring Setting - The ring settings are used to change the position of the internal wiring relative to the rotor.
Ringstellung - German for "ring setting".
Rotor - Rotatable disc with 26 electrical contacts arranged in a circle joining one face to another in a scrambled pattern.
Rotor period - Number of keystrokes for a complete cycle (e.g. 26x25x26 = 16900 for a 3 rotor Enigma).
Schreibmax - An optional printer attachment for the Enigma.
Static wheel - See Entry stator.
Static rotor - See Entry stator.
Stator - See Entry stator.
Stecker - Plug.
Steckerbrett - Plug board (sometimes referred to as "steckerboard").
Steckerverbindungen - Plug board connections.
Stop characters - Symbols (typically an "X"), used to separate words in a message.
Thin reflectors - Reflectors used with the Greek wheels.
UKW - See Umkehrwalze.
Umkehrwalze - Reflector (German for reversing drum).
Walzen - Wheels or rotors.
Walzenlage - German for "wheel order", referring to rotors.
Wheel Order - The order or the three or four rotors.
Zusatzwalze - See Greek wheel.