IPA: /ˈɡaɪdə/
KK: /ˈɡaɪdər/
A person who leads or directs others, often providing advice or assistance.
The guider helped us navigate through the complex trails in the forest.
Guider is formed from "guide" (from Old French *guider*, meaning to lead or direct) and "-er" (meaning a person who). A guider is a person who leads or directs others.
Think of someone who 'leads' ('guide') others — the '-er' just means a person. A guider is someone who helps others find their way.