Wordnet 3.0
VERB (2)
1. 
 make an addition; 
- Example: "Let's add on to this"2. 
 add to the very end; 
- Example: "He appended a glossary to his novel where he used an invented language"[syn: append, add on, supplement, affix]
WordNet (r) 3.0 (2006):
add on
    v 1: make an addition; "Let's add on to this"
    2: add to the very end; "He appended a glossary to his novel
       where he used an invented language" [syn: append, add on,
       supplement, affix]