| 释义 |
- Transportation
- Military
- Other
M21 or M-21 may refer to: Transportation- M21 (New York City bus), a New York City Bus route in Manhattan
- M-21 highway (Michigan), a road connecting Flint and Grand Rapids
- Highway M21 (Ukraine)
Military- HMS M21, Royal Navy M15 class monitor; sunk in 1918
- M21 mine, an American circular anti-tank landmine
- M21 Sniper Weapon System, a sniper rifle based on the M14 rifle
- Zastava M21, a Serbian assault rifle
- the carrier aircraft for the Lockheed D-21
- M21 Mortar Motor Carriage, a Half-Track carrying an 81mm Mortar
Other- BMW M21, a 1983 2.4 L diesel straight-6 engine
- MSrE M-21, Hungarian aerobatics aircraft
- Lockheed M-21, an American reconnaissance drone carrier aircraft
- Messier 21, an open star cluster in the constellation Sagittarius
- M postcode area, M21 Chorlton-cum-Hardy, Firswood area of Manchester
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