The word "rucks" can be used as a noun or a verb. As a noun, it means a bag carried on the back, especially by soldiers. As a verb, it means to gather or crumple something together. There are numerous synonyms for this word that can be used depending on the context. Synonyms such as backpack, knapsack, haversack, and pack are often used to refer to a bag carried on the back. Other synonyms for the verb form of the word "rucks" include bunch, scrunch, gather, crumple, and tuck. These words can be used interchangeably to provide more variety and depth to one's writing.