Crack
Crack frequently refers to: 

Crack, a fracture in a body
Crack, a fracture (geology) in a rock
Crack, short for crack cocaineCrack may also refer to:

Art, entertainment, and media
Cracks (film), a 2009 independent thriller
Crack Movement, a Mexican literary movement
Crack (band), a Spanish progressive rock group
Crack (album), an album by Z-RO
Cracks (album), an album by Nabiha
The Crack, first album by The Ruts
Crack Magazine, a UK-based European music and culture monthly
The Crack (magazine), a free culture magazine covering the North East of England

Slang
Crack, carrack

Gaining entry
Safe cracking, the process of opening a safe without the combination or the key

Software
Crack (password software), a UNIX/Linux password hacking program for systems administrators
Software cracking, a computer program that modifies other software to remove or disable features usually related to digital rights management
No-disc crack, software to circumvent Compact Disc and DVD copy protection
Password cracking, the process of recovering passwords from data stored in or transmitted by a computer system
Security hacker, cracking a system to gain unauthorized access (sometimes mislabeled as "hacking")

Other uses
Cracking (chemistry), the process whereby complex organic molecules are broken down into simpler molecules
Crack spread, the value difference between crude oil and oil products or between different oil products, usually expressed as a per-barrel value
CRACK, an acronym for 'Children Requiring A Caring Kommunity', now called 'Project Prevention'
CRACK International Art Camp
Craic, or crack, an Irish term for discourse, news, etc.

See also
CRAC (disambiguation)
Crack-Up (disambiguation)
Cracker (disambiguation)
Cracking (disambiguation)
Crak!, 1963 pop art lithograph by Roy Lichtenstein
Krack (disambiguation)
Krak (disambiguation)