The word "枯树" is formed by combining the character "枯", meaning withered, which is a phono-semantic character with "木" (wood) as its semantic radical and "古" as its phonetic component, and the character "树", meaning tree, also a phono-semantic character with "木" as its semantic radical and "对" as its phonetic component; together they create a modifier-noun compound where "枯" describes the state of "树", resulting in the meaning "withered tree".