(nautical) A muzzleloading gun capable of firing shells weighing sixty-four pounds

plural of 64-pounder

(computing) A superset of the x86 instruction set architecture, providing additional support for 64-bit addressing while remaining mostly backward compatible with older applications.

Alternative spelling of x86-64

(computing) An EPIC 64-bit instruction set architecture designed to allow relatively simple, cheap CPUs to execute many 64-bit instructions simultaneously and with potentially very high performance; developed by Intel in the late 1990s with the intent of replacing the older x86 architecture, but was delayed and proved uncompetitive with x86 (especially x86-64), seeing use only in Intel's own Itanium line of high-end CPUs.

(computing, networking) an obsolete EUI which originally encompassed both MAC-48 and EUI-48 identifiers by a simple translation mechanism

(music) A note whose duration is one sixty-fourth that of a whole note.

plural of 64th note

(paper, printing) A size of paper or book: 1.87"-2.5" x 2.5"-3.125".

plural of 64mo