dlの中にdivを入れて作るレイアウト

<div class="clearfix">
<dl class="definition_list">
<div>
<dt>項目1</dt>
<dd>内容1</dd>
</div>

<div>
<dt>項目2</dt>
<dd>内容2</dd>
</div>

<div>
<dt>項目3</dt>
<dd>内容3</dd>
</div>

<div>
<dt>項目4</dt>
<dd>内容4</dd>
</div>

<div>
<dt>項目5</dt>
<dd>内容5</dd>
</div>

<div>
<dt>項目6</dt>
<dd>内容6</dd>
</div>
</dl><!-- /.definition_ist -->
</div>

dl.definition_list{
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    text-align: left;
}
dl.definition_list div{
    width: 48%;
    margin: 0;
    padding: 0;
}
dl.definition_list dt{
    float: left;
    width: 80px;
    padding: 10px 0;
    border-top: solid 1px #A5A5A5;
    font-size: 12px;
    font-weight: bold;
}
dl.definition_list dd{
    float: left;
    width: calc(100% - 80px);
    padding: 10px 0;
    border-top: solid 1px #A5A5A5;
    font-size: 12px;
}
/* 768px以下 */
@media only screen and (max-width: 48em) {
dl.definition_list{
    display: block;
}
dl.definition_list div{
    width: 100%;
}dl.definition_list dt{
    font-size: 10px;
}
dl.definition_list dd{
    font-size: 10px;
}
}
/* floatがあるのでclear */
.clearfix::after {
  display: block;
  visibility: hidden; 
  clear: both;
  height: 0;
  content: "";
}