I agree, terminology is important, and “collateral damage” doesn’t mean attacking civilian targets and “accidentally” killing the civilians inside them.
It means attacking a MILITARY target, and accidentally killing civilians because there was no reasonable way to attack that MILITARY target without risking the lives of civilians.
Unless the airport attacked was a military one (I don’t believe it was, it was the normal international one) then the term collateral damage doesnt apply and it was an attack on civilians. That’s the very definition of terror.
The IRA didn't generally target civilians, but instead, went for targets that they defined as legitimate, including economic targets - so would you say they weren’t terrorists? At least they gave warnings to evacuate civilians which the Houthis don’t do.