Double field module theming
If you are using default (Unformatted list) formatter override double-field-item.html.twig template with the following markup:

&lt;dt&gt;{{ item.first }}&lt;/dt&gt;&lt;dd&gt;{{ item.second }}&lt;/dd&gt;


Note that Double field ships with HTML list formatter which may render definition list so you might not need to override anything.