This expression refers to something that is accomplished without difficulty or somebody who is easily persuaded or defeated. Often times people who are too nice, wish to avoid conflict, or cannot stand up for themselves are 'pushovers,' and may be manipulated by others to do what they want. However, it is important to note that somebody regarded as a 'pushover' may not necessarily be easily persuaded or defeated by everyone and in all situations. For example, in a professional context, you may only be a 'pushover' when it comes to your boss, or, in a social context, when it comes to your children. Phrases with a similar meaning include 'walkover,' and 'a piece of cake.'