1. mess, rubbish, junk [noun] [de troep, no plural]

"Troep" is what you typically find in your attic: old junk. Quite a few synonyms exist for "troep" (see ‘Related words’). "Troep" is also used to describe a disorganised state of a room or place, or – by some people – of a hairdo: the so-called "Coupe troep" ("Messy haircut") 😉

Examples:
– "Zijn kamer is één grote troep omdat hij nooit opruimt."
("His room is one big mess bacuse he never tidies it".)

– "Heb je nog oude troep die ik op de rommelmarkt kan verkopen?"
("Do you have any old junk that I can sell on the rummage sale?")

– "Wat een troep! Halen ze het vuilnis niet op in dit land?"
("What a mess! Don’t they collect the garbage in this country.")

Related words: 
– Bende: mess [noun] [de bende, no plural].
– Rotzooi: junk [noun] [de rotzooi, no plural].
– Zooi: mess [noun] [de zooi, no plural]. Also the diminutive is very common: zooitje.
– Rommel: junk [noun] [de rommel, no plural].

2. troop, body of soldiers [noun] [de troep, de troepen]

"Troep" – more often used in the plural ‘troepen’ – also has a totally different meaning: a group of soldiers. Beside the more cheerful news on the Olympic Games, you’ll probably find this word in the headlines of this week’s newspapers.

Examples: 
– "<Voorpagina van NRC vanochtend:> ‘Russische troepen verlaten Gorï’."
("<Front page of NRC this morning:> ‘Russian troops leave Gori’.")

– "De VN pleiten de inzet van vredestroepen in deze regio."
("The UN pleads for the deployment of peace troops in this region.")

Related words: 
– Vredesmacht: peacekeeping force [noun] [de vredesmacht, de vredesmachten].
– Leger: army [noun] [het leger, de legers].