<div class="flipCard"> 
  <div class="card" onclick="this.classList.toggle('flipped');"> 
    <div class="side front">Keyword</div> 
    <div class="side back">Definition<br/>Explanation</div> 
  </div> 
</div> 

.flipCard {
  -webkit-perspective: 800;
  -ms-perspective: 800;
  -moz-perspective: 800;
  -o-perspective: 800;
   width: 400px;
   height: 200px;
   position: relative;
   margin: 50px auto;
}
.flipCard .card.flipped {
  transform:rotatey(-180deg);
  -ms-transform:rotatey(-180deg); /* IE 9 */
  -moz-transform:rotatey(-180deg); /* Firefox */
  -webkit-transform:rotatey(-180deg); /* Safari and Chrome */
  -o-transform:rotatey(-180deg); /* Opera */
}
.flipCard .card {
  width: 100%;
  height: 100%;
  -webkit-transform-style: preserve-3d;
  -webkit-transition: 0.5s;
  -moz-transform-style: preserve-3d;
  -moz-transition: 0.5s;
  -ms-transform-style: preserve-3d;
  -ms-transition: 0.5s;
  -o-transform-style: preserve-3d;
  -o-transition: 0.5s;
  transform-style: preserve-3d;
  transition: 0.5s;
}
.flipCard .card .side {
  width: 100%;
  height: 100%;
  padding: 10px;
  cursor: pointer;
  position: absolute;
  box-sizing: border-box;
  z-index: 2;
  backface-visibility: hidden;  /* W3C */
  -webkit-backface-visibility: hidden; /* Safari & Chrome */
  -moz-backface-visibility: hidden; /* Firefox */
  -ms-backface-visibility: hidden; /* Internet Explorer */
  -o-backface-visibility: hidden; /* Opera */
  box-shadow: 0 0 10px rgba(0,0,0,0.6);
  overflow: auto;
}
.flipCard .card .back {
  background: white;
  color: black;
  transform:rotatey(-180deg);
  -ms-transform:rotatey(-180deg); /* IE 9 */
  -moz-transform:rotatey(-180deg); /* Firefox */
  -webkit-transform:rotatey(-180deg); /* Safari and Chrome */
  -o-transform:rotatey(-180deg); /* Opera */
}

.flipCard .card .front {
  font-family: Georgia;
  font-size: 3em;
  text-align: center;
  line-height: 160px;
  background-color: #7030a0;
  border: 3px solid white;
  color: white;

}
.flipCard .card .back {
  background-color: #dbb2f9;
  border: 3px solid white;
  text-align: center;
  color: black;
  padding-top: 50px;
  font-family: Georgia;
  font-size: 2em;
}