Intriguing
Part of speech: adjective
Definition: Causing a desire to know more; mysterious.
Part of speech: verb
Definition: To conceive or carry out a secret plan intended to harm; to form a plot or scheme.
Example sentence: I'd paint long strips of canvas and abandon them on the beach, or put bread out in geometric patterns for the pigeons downtown. I wanted people to find something nice and intriguing to puzzle over. Then I'd go back to see if the things were still there, or if anyone would notice.
Challenging
Part of speech: verb
Definition: To invite (someone) to take part in a competition.
Part of speech: adjective
Definition: Difficult, hard to do.
Example sentence: Each one of us has our own evolution of life, and each one of us goes through different tests which are unique and challenging. But certain things are common. And we do learn things from each other's experience. On a spiritual journey, we all have the same destination.