It's a phrase used to describe people. If someone is wishy-washy, they change their opinions, beliefs, or desires too much. For example, if you have a friend who is wishy-washy and you ask them what they want to do this next weekend, they will change their mind a few times before the weekend comes.

wkwkwkkw Mr. Carkner.. i found that expression when i read sth from internet :D

Haha, I love this expression. It just means that someone is unreliable, flaky and inconsistent, as the person below said.