The term FALLEN TREE can be broken down into three words: FALLEN, TREE, and LOG. The word FALLEN is an adjective that describes something that has been knocked down or has collapsed. The word TREE is a noun that refers to a large plant with a trunk and branches. The word LOG is a noun that refers to a section of a tree trunk that has been cut or FALLEN off. Together, the three words describe a tree that has been knocked down or has collapsed and has had a section of its trunk cut off.