Pant sniffer
A term which refers to a person who has a strong interest, even obsessive, in niche subjects. This interest may be not understood by the general public. Also referred to as a nerd or anorak.
The steam train went under the bridge. All the pant sniffers were there taking photos.
pant sniffer
A derogatory term for someone you very much dislike, and are suggesting that they spend their spare time sniffing the inside seam of worn pants.
Going to that party sounds good, but that Peter will be there and he's a right pant sniffer