1. Without advance preparation
   - ad lib, spontaneously, impromptu

Encyclopedia: Ad libitum

• fress
• fret
• fretful
• fretfully
• fretfulness
• fretsaw
• fretted
• fretwork
• Freud
• Freudian
• Freudian psychology
• Freudian slip
• Frey
• Freya
• Freyja
• Freyr
• FRG
• Fri
• friability
• friable
• friar
• friar preacher
• friar's lantern
• friar's-cowl
• friary