Explanation:

- Plagiarism refers to the act of using someone else's work or ideas without proper acknowledgment and claiming them as your own.

- Option 1: There was an epidemic of plague in the area.

- This is related to illness and disease, not intellectual property.

- Option 2: It is a sort of political philosophy.

- This doesn’t connect with the concept of copying or intellectual theft.

- Option 3: It indicates a happy community spirit like in playing Holi.

- Holi is a festival, unrelated to the concept of claiming someone else's work.

- Option 4: It is presenting the work of someone else as one's own.

- This is the correct definition of plagiarism.