(poor) excuse, pretext, fib [noun] [de smoes,de smoezen] 
A "smoes" is an informal synonym for "excuus", which translates to "excuse". It is usually a (small) story that is used to twist or cover up the truth. Although "smoes" has a negative connotation in this sense, it is not as ‘bad’ as a straight lie (which translates to "leugen" in Dutch).
Besides "smoes" you will often see its diminutive "smoesje" which makes it even less bad than a "smoes":-)
The related verb is "smoezen", which translates to "to whisper (secretly)".
Examples:
– "Ik verzin geen smoes, dit is echt de waarheid!" 
("I’m not making up an excuse, this is really the truth!")
– "Frank is weer laat vanochtend." – "Wat is nu zijn smoes?"
("Frank is late again this morning." – "What’s his excuse now?")
– "Geen smoesjes, jongedame! Niet smoezen in de klas!"
("No excuses, young lady! No secret whispering during class!")
Expressions:
– "Een leugentje om bestwil": a white lie.
– "(Ja ja,) smoesjes!": yeah right, that’s just making poor excuses!
Related words:
– Excuus: excuse [noun] [het excuus, de excuses].
– Uitvlucht: pretext, escape, excuse [noun] [de uitvlucht, de uitvluchten].
– Leugen: lie [noun] [de leugen, de leugens].
– Liegen: to lie [verb] [loog, gelogen].
Jongens!
The Dutch word “escuus” does not exactly translate to the word “excuse” in (American) English. Rather, a better English equivalent is a “fib”, something close to a “white lie.” Smoes=fib. A common use of “excuse” in English: Teacher — why isn’t your work ready? What’s your excuse (explanation)? Student– my excuse is that I didn’t have time (or that my dog ate my homework, which probably is a smoesje). allemaal imho, vanzelfsprekend.
Thank you H,
I added “fib” as a possible translation of smoes.
Regards,
Marc