1. smooth, slippery [adjective/adverb] 
In general, "glad" refers to an object which is not rough. It is often used when warning for slippery roads in wintertime, or to describe objects with a smooth surface.
Examples:
– "Het tijdschrift heeft een glanzende, gladde voorkant."
("The magazine has a shiny, smooth cover.")
– "Puisterige pubers gebruiken clearasil om een gladde huid te krijgen." 
("Teens with pimples use clearasil to get a smooth skin.")
– "Mijn fietsbanden hebben bijna geen profiel meer; ze zijn helemaal glad."
("My bicycle-tyres don’t have any tread left; they’re all bald.")
– "De gladde wegen leidden tot lange files op de snelwegen."
("The slippery roads resulted in long traffic jams on the highways.")
– "De sneeuw maakte de weg spiegelglad."
("The snow made the road as slippery as glass.")
Expressions:
– "Iets glad vergeten": to totally forget something.
Example:
– "Het spijt me heel erg, maar ik ben je verjaardag glad vergeten."
("I’m so sorry, but I totally forgot your birthday.")
Related words:
– Spiegelglad: as slippery as glass [adjective/adverb].
2. slick [adjective/adverb]
"Glad" can also refer to boys or men. If so, it is seldomly used as a compliment. Someone is "glad" when he’s not to be trusted. I suspect the origin of the word has something to do with an apparent correlation between untrustworthy men and the exuberant amounts of hair gel that these men tend to use to create their slick hairdo. Slightly old-fashioned words for such a type of man are "gladjakker" and "gladjanus".
Examples:
– "Ik zou mijn auto niet van die autohandelaar kopen; hij is veel te glad."
("I wouldn’t buy my car from that car dealer; he’s way too slick.")
– "Kijk maar uit voor die gladde jongens met hun gladde praatjes."
("You’d better watch out for those slick guys with their slick stories.")
Related words:
– Gladjanus: slicker [noun] [de gladjanus, de gladjanussen].
– Gladjakker: slicker [noun] [de gladjakker, de gladjakkers].
I just found your site a few weeks ago – thank you – it is fun for me to keep my Dutch current.
Suggestions on this post
1. Puisterige may translate better to blemished – or one might say teens with pimples
2. Banden zonder profiel in English may translate better as bald tires (like a bald head)
Dear Jack,
glad you like the dwotd 😉
Thanks for your suggestions! Our objective is to learn people some Dutch words; we assume most people understand our imperfect English 😉
Laura
Need some help. I am trying to wish a friend Happy Thanksgiving in Dutch I tried the online translator but I don’t think what I was offered is corret. This is what I was given Gelukkige Dankzegging.
Thank you for your assistance,
Kevin
Hi Kevin,
“Thanksgiving” is not a holiday in the Netherlands. As such, there’s no translation for Thanksgiving in Dutch. Most Dutch know Thanksgiving though. “Gelukkig Dankzegging” is the literal translation. Your Dutch friend will probably understand “Happy Thanksgiving” better than “Gelukkige Dankzegging” 🙂 You could go for the Dutch-English combo: “Ik wens je een fijne/gelukkige/feestelijke Thanksgiving” (I wish you a nice/happy/festive Thanksgiving)…
Hope this helps, regards,
Marc
Thanks Marc I am sure this will put a smile on her face.
Ik wens je een gelukkige
Kevin
Hello
Glad: 2 slick
I found great the association of glad with the guys’ hair gel.
For me with glad-slippery, I think about soap, fish, something that cannot be caught, slips from your hands. Therefore, I think about a thief, a con man, an impostor, and as an adjective: sly, astute, cunning, crafty, insidious, slippery, smart, tricky, wily, etc.
Regards,
Maia
Old English glæd “bright, shining, joyous”. Words are alive! Words change! What do you think of nice from latin nescius “who does not know”, provençal nice “stupid” English “nice”.
We call it “Kalkoendag.” 😉