erikw/jekyll-glossary_tooltip

/* Tooltip from https://www.w3schools.com/css/css_tooltip.asp */
.jekyll-glossary {
  position: relative;
  display: inline-block;
  border-bottom: 3px dotted blue;
  cursor: help;
}

.jekyll-glossary .jekyll-glossary-tooltip {
  visibility: hidden;
  width: 120px;
  background-color: black;
  color: #fff;
  text-align: center;
  font-size: 0.5em;
  padding: 5px;
  border-radius: 6px;

  /* Position the tooltip text - see examples below! */
  position: absolute;
  z-index: 1;

  width: 160px;
  bottom: 100%;
  left: 50%;
  margin-left: -80px; /* Use half of the width to center the tooltip */

}

/* Show the tooltip text when you mouse over the tooltip container */
.jekyll-glossary:hover .jekyll-glossary-tooltip {
  visibility: visible;
}

/* Style the source link (if there is one provided in the glossary entry). */
.jekyll-glossary-source-link:before {
  content: "[source]";  // "(reference)", "<link>" or whatever you want.
}