adjective

1. of, at, or forming a base; fundamental; essential
2. constituting a basis or introduction; elementary basic military training
3. 1. Chem. of, having the nature of, or containing a base; alkaline
   2. designating, of, or resulting from a process of manufacturing steel from high-phosphorus iron, in which the refining agent is a basic slag formed from a basic furnace lining and the addition of lime
4. Geol. designating or of igneous rocks with 45-52% silica

noun

1. a basic principle, factor, etc.: usually used in pl.
2. basic military training