This is the 2364th most frequent Chinese word.
军军
"军军" is not a standard Chinese word; it may be a reduplication of "军" (army/military) or a name.
In this sentence, '军军' is used as a proper noun, such as a name referring to an individual.
军军喜欢踢足球。
Jun Jun likes to play football.
Here, '军军' again appears as a name, and the context clarifies its use and association with the topic of the military.
军军正在读一本关于军事的书。
Jun Jun is reading a book about the military.
The name '军军' represents a participant in the conversation and indicates a direct interaction.