If you're feeling tetchy, you're irritable or easily annoyed. Stepping in a puddle on your way to school and spending the whole day with cold, wet socks might make you tetchy.
Is your brother cranky and no fun to be around today? He's tetchy. This adjective is similar to words like testy, peevish and grumpy. It's another way to describe your fractious friend or your snappy sister. The origin of tetchy is unclear, but most experts suspect it comes from the Scots word tache, "blotch" or "fault."