Hash table, a data structure associating keys with values using a hash function

Hash House Harriers, a loosely-organized group of social organizations focused on running and camaraderie; also referred to as "hashing"

Hashish, a psychoactive drug derived from the Cannabis plant

Cryptographic hash function, a hash function suitable for use in information security

Number sign, #, also called "pound sign" in the USA

Hash function is a small digital "fingerprint" made from any kind of data. Some types are:

Associative array, an abstract data type often implemented as a hash table

Geometric hashing, a method for efficiently finding geometric objects of the same or similar shape

Hash mark, in mathematics, sometimes called a tick mark, is a short line perpendicular to an axis in analytic geometry

Hash Bash, an annual event in Ann Arbor, Michigan

Service stripe, commonly called a hash mark, is a decoration of the United States military

Hash marks, in ice hockey, two pairs of parallel lines on either sides of the face-off circles

Hash (food), a coarse chunky mixture of beef and other things, e.g. corned beef hash; cf. Hash brown