See examples of mysterious used in a sentence. How to use mysterious in a sentence. Full of, characterized by, or involving mystery. He died in mysterious circumstances. Definition of mysterious adjective in oxford advanced learners dictionary. Someone or something that is mysterious is strange and is not known about or understood. This is reminiscent of the extraordinary relationship which amputees develop with their artificial replacements, revealing a whole inner โ€ฆ Meaning, pronunciation, picture, example sentences, โ€ฆ The meaning of mysterious is of, relating to, or constituting mystery.