Raise your hand if you know what Throwback Thursday means.

About.com tells me — and any of you who didn’t raise your hand — that it’s “the name of a weekly social media posting trend game that users participate in to share and look back fondly on some of their favorite memories.”

With all these 21st century words that are being thrown at us of a certain age, it got me thinking nostalgically of words that no longer have a place in our language. So, here are some “old school” words that have passed so far from our lexicon that college students age 25 or younger, when recently asked, had no clue of their meaning.

Penny candy: The students’ best guess? Penny candy was an actress. XXX-cuse me if I don’t mention which type of film she would star in. I hear “penny candy” and I immediately taste fruit slices, Annie Rooneys, Boston drops, Trilby cuts and Humbugs.

Green stamps: I remember when the S&H Green Stamps’ reward catalogue was the largest publication in the U.S. The students’ response? “Like what they do at Disneyland when you want to re-enter?”

Rumble seat: They thought it had something to do with professional wrestling. This flesh jiggling exterior seat at the rear of a jalopy finally disappeared in 1949.

Gams: Our generation’s slang for a nice pair of female legs. Their guess? “That orange potato thing.”

Galoshes: Them: “Aren’t those the eyelashes sold by Lady Gaga?” If you grew up in any state east of Arizona, you must remember the rubber outer shoes worn in the rain or snow.

Instamatic: As ubiquitous as our cell-phone cameras are now, remember the easy-load cartridge “Pocket Instamatics” when you wanted to grab a moment? The students guessed “Instamatic” was some sort of coffee machine.

Mary Janes: They had no idea about the tooth-extracting peanut butter and molasses candy or the children’s shoes. Their guess was “something you smoke at a party.”

Mercurochrome: Try describing the orange chicken-like glow of the topical antiseptic now banned because of its mercury content. One student thought that it might be a science fiction movie from the ’50s.

Service station: “A place you visit in Las Vegas,” one student joked.

Bouffant: Remember those ’60s beehive-hairstyles balancing on top our heads? The closest student guess was a puffy shirt — like those made famous by Seinfeld.

Rabbit ears: Students thought the top-of-the television antenna that brought in VHF signals was something you ordered in a restaurant — like buffalo wings.

LOOK: “At what?” was all they could say when they heard the name of the magazine that biweekly sold 7.75 million copies.

Oh well, despite the vast new knowledge of the under-25 set, I still think these 20th century “old school” words are very cool.

Well, maybe I shouldn’t use the word “cool” (year of origination: 1930). Neat (1806)? Just dandy (1794)? Nifty (1865)? I think I’ll go with my 21st century buds (translation: pals) and just say, “They’re sick!”

Until next time … keep thinking the good thoughts.

— For more than 30 years, Rona Barrett was a pioneering entertainment reporter, commentator and producer. Since 2000, she has focused her attention and career on the growing crisis of housing and support for our aging population. She is the founder and CEO of the Rona Barrett Foundation, the catalyst behind Santa Ynez Valley’s first affordable senior housing, the Golden Inn & Village. Contact her at info@ronabarrettfoundation.org. The opinions expressed are her own.