When you snuffle you breathe in a sniffly, stuffed-up way through your nose. People are most likely to snuffle when they're crying or have a bad cold.
For some people, spring means warmer weather and pretty flowers, but for others it means their allergies make them snuffle and sneeze continuously. When you see a sad movie in a theater, you'll probably hear people snuffle all around you — and if you visit the zoo or a farm, you can watch animals snuffle, or sniff at things. The Old English version of snuffle is snofl, "phlegm or mucus."