rattletrap

1. not comparableMechanically unreliable or in disrepair.

   BLANCHE:What you are talking about is brutal desire--just--Desire!--the name of that rattle-trap streetcar that bangs through the Quarter, up one old narrow street and down another...

   1947, Tennessee Williams, A Streetcar Named Desire, Scene Four

   2 more examples

   2006, Paul McGeough, Bush 'palace' shielded from Iraqi storm, theage.com.au, August 26, http://www.theage.com.au/news/world/bush-palace-shielded-from-iraqi-storm/2006/08/25/1156012740594.html, All services for the biggest embassy in the world will operate independently from the rattletrap utilities of the Iraqi capital. (speaking of the new US Embassy in Baghdad)

   Every cultural instinct and previous experience tells you that when you travel this far you should find, at the very least, people on camels. There should be unrecognizable lettering on the signs, and swarthy men in robes drinking coffee from thimble-sized cups and puffing on hookahs, and rattletrap buses and potholes in the road and a real possibility of disease on everything you touch—but no, it's not like that at all.

   2000, Bill Bryson, In a Sunburned Country, page 10

plural rattletraps

1. informalA mechanical device, particularly an automobile, that is worn out, run down, or mechanically unreliable as indicated by noises it makes in operation.

   Mom always worried about our safety in my friend's rattletrap. I told her not to worry, as it can't go fast enough to be dangerous.

   Synonyms: banger, bucket of bolts, banger, beater, bucket of bolts, bucket of rust, clunker, crate

2. datedAny piece of miscellaneous equipment or junk.

   And they tumbled about the rattletraps under the cupboard, and rummaged the drawers in search of the sacred volume.

   1863, Sheridan Le Fanu, The House by the Churchyard

3. A type of noisemaker in which the teeth of a gear repeatedly bend and release a stiff tongue.
4. datedderogatoryslangA person's mouth.

   Shut your rattletrap!

   Synonyms: trap, yap