Feminism is a broad subject with many valid definitions. Among them the most popular and widely accepted is that it is the radical notion:
"that women are in fact human beings with the same basic human rights and needs for self fullfillment as men."
A definition that might seem flat and dumb to the less educated masses who might not consider the short historic period this has been an accepted idea. (some are still arguing.)
There are many challenges yet to conquer for the modern feminist, you need only take a look at the other definitions offered at this very site to get a general feeling for the hassle and dicrimination a woman or man feminist might encounter daily.
Next time ignorant suckers bemoan the fact that they no longer have the legal responcibility of the woman they choose to mary, the fact that they no longer have to fear getting a girl pregnant each time they have sex and the fact that they can afford the newest wide screen tv because their significant other was able to chip in cause she's like getting payed soon to be eaqually at her job. Take a time to think about what feminism gave you for free while you was busy scratching your balls and feeling underprivileged.