feetfirst

/ˈfitˌfɜrst/
adverb
  1. With the feet going in first; headlast.
    • The diver jumped feetfirst into the pool.
    • The baby slid down the slide feetfirst.
    • He entered the water feetfirst to avoid hitting his head.
  2. In a direct or headlong manner, often without caution.
    • He went feetfirst into the argument without thinking.
    • The company dove feetfirst into the risky market.
    • She jumped feetfirst into the new project without planning.
Antonyms