gaffe or (rare) gaff /gaf/

A blunder

• plane-polarised
• plane-polarized
• planer
• planers
• planes
• plane sailing
• planet
• plane table
• plane tabled
• plane tables
• plane tabling
• planetaria
• planetarium
• planetariums
• planetary
• planetary gear
• planetary gears
• planetary nebula
• planetary nebulae
• planetesimal
• planetesimals
• planetic
• planetical
• planetoid
• planetoidal