Initialism of accelerated reply mail (a service of the United States Postal Service) / Initialism of adjustable rate mortgage.

(computing) Initialism of Acorn RISC Machine or Advanced RISC Machine.

(of two or more people) With arms linked together; with arms around each other's shoulder or waist. / (figuratively) In collusion, in concert (with someone).

Alternative form of arm in arm

The portion of the upper human appendage, from the shoulder to the wrist and sometimes including the hand. / (anatomy) The extended portion of the upper limb, from the shoulder to the elbow.

(obsolete) To take by the arm; to take up in one's arms.

(UK dialectal, chiefly Scotland) Poor; lacking in riches or wealth. / (UK dialectal, chiefly Scotland) To be pitied; pitiful; wretched.

(usually used in the plural) A weapon. / (in the plural) Heraldic bearings or insignia. / (in the plural, obsolete) War; hostilities; deeds or exploits of war.

(transitive) To supply with armour or (later especially) weapons.

(sometimes in combination) Equipped, especially with a weapon. / (of a weapon) Prepared for use; loaded. / (obsolete) Furnished with whatever serves to add strength, force, or efficiency.