A weebtard is a weeaboo (White person obsessed with japanese culture and anime) who is also retarded. One may argue that all weeaboos are retarded; suggesting all weeaboos are then weebtards. That would be correct.

When you think up something brilliantly righteous while baked.

An individual who has transcended the normal cringyness of weeabou a is quite mentally delayed in their way of thought process