What is the best way to exclude an array of entries?
Craft documentation describes how to exclude entries with a given value. In this case, we want a string that looks like: 'and, not id1, not id2, not id3, not id4'

So we need a string that is all of the featured article ids separated by , not. First, get them as an array using ids():

{% set featuredArticleIds = craft.entries.section('articles').featured(1).limit(4).ids() %}


Then convert that array to a string, using twig's join filter:

{% set featuredArticleIdsString = featuredArticleIds | join(', not ') %}


Then, fetch all the articles, but not the featured ones:

{% set notFeaturedArticles = craft.entries.section('articles').id('and, not '~featuredArticleIdsString) %}


[thanks to carlcs for crucial fix]