A set of letters has been replaced by $a$, $b$, $c$, and $d$.
Following are some of the words that consist of those letters, and their meaning:
$abc = a\ title\ (n.)$
$abcd = a\ title\ > abc\ (n.),\ give\ cbad\ to\ (v.)$
$Dcba ⊂ (a\ title\ > abcd)\ (n.)$
$Dcba = Represents\ what\ often\ comes\ before\ or\ after\ bcd\ (n.)$
$bcd = ARGHH!\ (n.)$
$cbad = move\ abc\ to\ abcd\ (v.),\ \land (v.)$
What are the letters that $a$, $b$, $c$, and $d$ replace, respectively?