There are continously question on what a domain hack is, or if a domain is a domain hack or not.
Below is a set of categories that constitute domain hacks. If you domain fits into any of the following categories, then you have a domain hack:
A domain where both sides of the dot combine to form a word,
A 1-word domain that can also form another word using its extension,
i.e. Box.es (Box and Boxes)
A subdomain that forms a word across itself, the name and the extension,
A subdirectory that forms a word across the name, the extension and itself,
A domain where both sides of the dot are each a word and form a phrase,
A domain where both sites of the dot form a short brandable “made up” word,
i.e. Bit.ly (commonly referred to as “Bitly”)
Partial subdomain hack
A subdomain that uses the subdomain and name only to work a word,
Split phrase hack
A domain where the last word in the hack is split across the dot,
*Note: Many do not consider this a domain hack so they aren’t very highly sought.
.al domains are well known for a large number of domain hack combinations. These domains are usually cheaper than other tlds.