delete

(delete item list &key test key)

The destructive counterpart of remove: returns list with every element matching item spliced out, modifying the cons cells in place rather than copying. The comparison is eql by default; the optional :test keyword takes a function designator to use a different comparison, and the optional :key keyword takes a selector function applied to each element before the comparison. Because the head of the list may change, always use the return value rather than relying on the original variable.