General difficulty:
* Elusive: Suggests someone who is hard to pin down or understand.
* Inscrutable: Implies a person who is mysterious and difficult to read.
* Unfathomable: Refers to someone whose thoughts and motives are impossible to understand.
* Opaque: Like a clouded window, it suggests someone who is unclear and hard to see through.
* Impenetrable: Means someone is very difficult to understand or get close to.
Specific to social interactions:
* Reserved: Describes someone who is quiet and reluctant to share personal information.
* Withdrawn: Indicates someone who is distant and emotionally unavailable.
* Aloof: Suggests someone who is detached and keeps people at a distance.
* Shy: Refers to someone who is uncomfortable with social interaction and avoids it.
Focus on personality:
* Complex: Means someone has many different sides and can be hard to understand.
* Contradictory: Suggests someone whose actions or words often seem to contradict each other.
* Paradoxical: Refers to someone who seems to be both contradictory and intriguing.
The best word to use will depend on the specific context and what you want to convey about the person.