1) Fodder is any character that is unimportant to a story. Fodders are usually nameless background characters. 2) A character that is by leaps and bounds inferior to another character. eg. Mizuki is fodder to Kakashi.
Basically a very weak person who has no importance to the plot or any battle going on like how almost 80.000 ninjas died from the juubi edo tensis and white zetsus and no one gave a shit but when neji died everyone went apeshit because he was important and was not weak fodder lol
Fodder is actually animal feed. But in slang terms it means someone that stands no chance and will be devoured easily. It is anyone or anything that does not stand a chance of succeeding.