The term has since been adapted (mostly in the West) to mean "robot anime" and is used to describe anime and manga series that center around robotic elements.
In mecha anime,the robots are usually vehicles or extensive, full-body "armor" piloted by humans and used in battle. Mecha components are typically quite advanced and offer a range of weapons as well as complete mobility and even flight capabilities and super-strength.
The size and appearance of the mecha robots vary, with some being not much bigger than the pilot who operates them while others are considerably larger, as in the case of the popular Transformer and Macross series. Some mecha also have an organic component to them, as in the case of the Evas used in Neon Genesis Evangelion.
Of course, mecha is not limited to anime and manga productions. Quite the contrary, many sci-fi movies and television shows have a strong mecha influence, with such notable works as Star Wars, War of the Worlds and Iron Man falling into this genre.