1. A person who writes music, especially an original composition:
* Merriam-Webster: "a person who composes music."
* Oxford English Dictionary: "A person who writes music, especially an original composition."
* Cambridge Dictionary: "a person who writes music, especially classical music."
2. A person who arranges or adapts music for performance:
* Merriam-Webster: "one that composes or arranges music."
* Oxford English Dictionary: "A person who arranges or adapts a musical work for performance."
3. A person who puts together or creates something, often using different elements:
* Merriam-Webster: "one who composes or puts together."
* Oxford English Dictionary: "A person who creates something by combining different elements."
Therefore, the dictionary definition of a composer is someone who writes, arranges, or creates music, often using different elements. The specific definition depends on the context of the word.