(noun) The repetition of meaning within a word, e.g. causeway, where both cause and way mean 'road'. Portmanteau (noun and adj.) A word made up of the blended sounds of two distinct words and combining the meanings of both, such as brunch. The term was first applied by Lewis Carroll to this type of word genesis.
The use of unnecessary or superfluous words. Poets often fall into this trap when trying to pad out a metrical line e.g. the clown's song from Shakespeare's Twelfth Night. When that I was and a little tiny boy, With hey, ho, the wind and the rain, A foolish thing was but a toy, For the rain it raineth every day.
Pleonasm is the use of more words (or even word-parts) than necessary to express an idea clearly. The word comes originally from Greek ("excess"). A closely related, narrower concept (some would say a subset of pleonasm) is rhetorical tautology, in which essentially the same thing is said more than once in different words.