from The American Heritage® Dictionary of the English Language, 4th Edition
- v. Usage Problem A past tense and a past participle of sneak. See Usage Note at sneak.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. Simple past tense and past participle of sneak.
The irregular form snuck originated by analogy of struck for the past of strike. Snuck was originally limited to a few dialects, but is now very widespread (especially in American English) and is recognized by most dictionaries. The word is now one of the best examples of irregularization of a regular verb, along with dove. (Wiktionary)