This p a p e r discusses an approach to incremental learning in natural language processing. The t e c h n i q u e of projecting and integrating semantic c o n s t r a i n t s to learn word definitions is analyzed as Implemented in the POLITICS system. E x t e n s i o n s and improvements of this technique are developed. The problem of generalizing existing word meanings and understanding metaphorical uses of words Is addressed In terms of semantic constraint Integration.