rmb

Short definition from Wiktionary

Verb

1. 1
   Pseudo-acronym of remember.

Noun

1. 1
   Initialism of roadside mailbox: part of a postal system used in rural areas where several houses collect their mail from a cluster of mailboxes at the roadside.
2. 2
   Initialism of Royal Marine Base.
3. 3
   Initialism of right mouse button.