Exclude from Dictionary

Optionally exclude words from the dictionary. From the Crossword Construction Kit window, click on Options | Exclude from Dictionary to access this feature. When spell checking the puzzle words or clues, the spell checker considers any words in the excluded list as misspelled and will prompt for verification.

Selecting this option presents a window that lists all words previously entered as words. Add or remove words from this list as needed. 

Crossword Construction Kit window > Options > Exclude from Dictionary