Muchacho is a Spanish word that is often used to refer to a young boy or teenager. However, there are several other synonyms that can be used in its place. For instance, the word "chico" can be used to refer to a young boy while "joven" can be used to describe a teenager. Another synonym is "niño," which can be used to refer to a young child or boy. Additionally, "adolescente" can be used to describe a teenager or young adult. Other synonyms for muchacho include "hombre joven," "jovenzuelo," "mozuelo," and "chaval." Depending on the context in which the word is being used, any of these synonyms may be appropriate.