あやしい means ‘suspicous’ and is actually a word I seem to find myself using quite a bit in Japan => useful!
I was walking towards some students slowly and one of them said something:
「What is that?」 I asked.
They said… 「あやしい」
I say, ‘Why?’
Answer: 「歩き方」 ＊_＊
After some thought I think the word was 不信者, someone you do not trust… (this was an incorrect guess at kanji through meaning).
[Credit to Miyo] 不審者 － is someone suspicious or doubtful