Third-rate means very bad in quality — not merely below average, but poor enough to be worth sneering at. It is a dismissive word, and the dismissal is the point: you use it when you want to look down on something, not when you are giving a fair report. It attaches most naturally to things people make or perform: a third-rate film, a third-rate hotel, a third-rate imitation, a third-rate poet. Used of a person it always judges their work, not their character — calling someone a third-rate lawyer says they are bad at law, not that they are a bad human being. It comes before the noun almost every time. The family is worth seeing whole: first-rate is genuinely good and is used often and warmly; second-rate means disappointing, not up to standard; third-rate is where contempt begins. There is no real fourth-rate — the counting stops, because by three the insult is already complete. The origin is naval: the Royal Navy once graded its warships as first-rate, second-rate and so on by how many guns they carried, and the ordinary language kept the ranking long after the ships were gone.