The word 'residual' is an adjective and this adjective can be used only before noun not independently. The meaning the word conveys is that of the something that remains at the end of the process. The synonymous term that can be used to convey the same idea is 'outstanding' and the sentence that can make the meaning of the term quite clear is following: You can still find some residual problems in that computer program. The sentence here conveys that there still remained some problem in the computer program that should be sorted out before you take it to the actual use.
There are some other words also that are formed from the same root and more or less convey the same idea. The words are residue, residuary and residuum.
There are some other words also that are formed from the same root and more or less convey the same idea. The words are residue, residuary and residuum.