slap

Concise Oxford English Dictionary © 2008 Oxford University Press:
slap/slap/

▶verb (slaps, slapping, slapped)

• 1 hit or strike with the palm of one's hand or a flat object.

  ■ hit against with the sound of such an action.

  ■ (slap someone down) informal reprimand someone forcefully.

• 2 (slap something on) apply something quickly, carelessly, or forcefully.

  ■ informal impose a fine or other penalty on.

▶noun

• 1 an act or sound of slapping.

• 2 informal make-up.

▶adverb (also slap bang) informal suddenly and directly, especially with great force.

■ exactly; right.

– phrases
slap and tickle Brit. informal playful sexual activity.
slap in the face an unexpected rejection or affront.
slap on the back a congratulation or commendation.
slap on the wrist a mild reprimand or punishment.

– origin ME: prob. imitative.