1. When you hit you penis against the vagina before inserting it for sex
2. When you wind it up to punch someone
3. When you first insert the penis for intercourse
EBK stands for "Elite Ball Knowledge." 1 In internet slang, "ball knowledge" originally referred to a deep understanding of football/soccer or basketball, but it has evolved into a broader term for having a highly sophisticated, deep, or niche understanding of any specific topic (such as music, movies, or subcultures).
Person A: "That scene was a direct homage to an unreleased 1982 Japanese indie film."
Person B: "Wow, EBK."