To chicken out.

Invented in the summer of 1964 by an eight year old San Diego elementary school Boy named Don who needed to find a new name that none of the bullies would recognize. The popular insult names at that time were Wimpy, from the "Popeye The Sailer" cartoon and Pussy from the obvious. Wussy and Wuss kept them confused for a short time and gave the abused a short victory over the bullies. In the beginning Don actually had them conviced it was a compliment. By 1972 it had become a real comon word at Clairemont High School and was later momorialized in the 1982 movie "Fast Times at Ridgemont High" that characterized those people at Clairemont High.

A common word used to say that someone is a pussy.

sissy, baby

A person who is physically weak and ineffectual. Often a male person with low courage factor.

A wuss is what one guy calls another guy when the first guy is too much of a pussy to call the second guy a pussy.

Someone with no balls