Kitchensink (or kitchen sink) is a term used to describe modpacks with a large amount of mods of no particular theme, and usually with just minor config changes. The word comes from the expression "everything but the kitchen sink."
Technic, the first major modpack, was a kitchensink modpack. Most early modpacks were kitchensink since there were relatively few mods such as MineTweaker and Hardcore Questing Mode that could control progression. Many of the most popular modpacks, such as Tekkit and FTB Infinity, are kitchensink modpacks. Kitchensink modpacks are often popular among servers, as they satisfy many different players' needs.