Birdbrain and Fair game

Birdbrain noun - A silly flighty person.

Fair game and birdbrain are semantically related. in fool topic. In some cases you can use "Fair game" instead a noun "Birdbrain", when it comes to topics like stupid or ridiculous person.

Fair game noun - A person who is the aim of an attack (especially a victim of ridicule or exploitation) by some hostile person or influence.

Birdbrain and fair game are semantically related. Sometimes you can use "Birdbrain" instead a noun phrase "Fair game".