skittish
Easily scared or jumpy, reacting nervously to sudden things.
Skittish describes someone or something that's easily startled, nervous, or jumpy. A skittish horse might bolt at sudden movements or loud noises. A skittish cat might hide under the bed when visitors arrive. When you feel skittish before giving a presentation, your heart races and you're on edge, ready to panic at the slightest thing going wrong.
The word often describes animals that are naturally wary or have learned to be cautious. A deer in the woods is skittish because staying alert to danger keeps it safe. But people can be skittish too. You might feel skittish walking into a room full of strangers, or skittish about trying something new like rock climbing.
Skittish isn't the same as being generally fearful or cowardly. It's more about being reactive and quick to startle. A skittish person or animal is constantly on alert, their nervous system primed to respond. Sometimes this comes from a bad experience: a dog that was once frightened by fireworks might become skittish around loud sounds. Other times it's just temperament. Some horses are naturally calm while others remain skittish no matter how gentle their training.