strange fantasm
mental fantasm
fleeting fantasm
A: Was that a real person I saw?
A：我刚才看到的是真人吗？
B: No, it was just a fleeting fantasm.
B：不，那只是一个转瞬即逝的幻象。
1) 幻象
2) 幻觉
3) 虚幻的事物
1. 幻象，幻觉
noun
1. An illusion or a mental image; something that is not real.
Synonym: phantasm, illusion