This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. Plural form of null.

v. Third-person singular simple present indicative form of null.

"Eventually they concluded that the Roman letters were so-called nulls, meant to mislead the code breaker, and that the letters represented spaces between words made up of elaborate symbols."

bull   

pulls    wools