To accost someone means to approach and speak to them in a bold, aggressive, or unwelcome way. If a stranger accosts you on the street asking pushy questions, they're not politely introducing themselves but confronting you in a way that feels uncomfortable or even threatening.

The word carries a sense of unwanted boldness. When someone accosts another person, they often ignore normal social boundaries about how to start a conversation. A reporter might accost a celebrity outside a restaurant, pressing for answers even when it's clear the person wants to be left alone. A salesperson might accost shoppers with aggressive pitches before they've even entered the store.

Accost usually suggests the person being approached didn't invite the interaction and probably wishes it weren't happening. It's different from simply “approaching” someone, which can be perfectly friendly and welcome. The word implies pushiness, forcefulness, and an invasion of someone's space and peace of mind.