NDB

English Wikipedia has an article on:

non-directional beacon

Wikipedia

English Wikipedia has an article on:

nuclear depth bomb

Wikipedia

NDB (plural NDBs)

1. (aviation) Initialism of non-directional beacon, a type of radiobeacon used in air navigation which transmits an omnidirectional radio signal containing no encoded information about the direction from an aircraft to the beacon.
2. (military, nautical) Initialism of nuclear depth bomb.

(navigational beacon):

• navaid

(nuclear weapon):

• depth charge

(navigational beacon):

• LOM

(navigational beacon):

• DME
• glideslope
• IGS
• ILS
• localizer, localiser
• marker beacon
  • fan marker, FM
  • inner marker, IM
  • middle marker, MM
  • outer marker, OM
• MLS
• TACAN
• VOR
• VORTAC

• BDN, DnB, BND, DNB, Dnb., DBN, NBD