NeoBundle 'ujihisa/ft-cmake'

You have indent/cmake.vim and syntax/cmake.vim, and also when you edit CMakeLists.txt the &filetype is "cmake".

<C-x><C-k> in insert mode to use dictionary completion (Vim's builtin feature.)

Keywords in dict/cmake.vim are from http://www.cmake.org/Wiki/CMake_Useful_Variables

• dict/cmake.txt

require 'nokogiri'
require 'open-uri'

x = open('http://www.cmake.org/Wiki/CMake_Useful_Variables').read
n = Nokogiri::HTML(x)
puts (n / 'dt').map(&:text).map(&:strip).sort

and some manual tweaks

GPLv3 or any later version.