dipstick

Most of the time, a dipstick is a simple tool: a thin rod (often metal or plastic) that you dip into a liquid to check the level. The most common example is the one used in cars to see how much engine oil you have. You pull it out, wipe it, dip it back in, and then look at the mark or line.

The word is also used as a mild insult. Calling someone a "dipstick" is an informal, often playful way to say you think they are being silly, clumsy, or not thinking clearly. You might say it when a friend makes a dumb mistake—like locking their keys in the car—but you would usually avoid it at work or with strangers.

A dipstick is, first of all, a tool for checking how much liquid is in something. It's usually a narrow stick or rod with markings on it. You dip it into the liquid, pull it out, and read the level from the wet line. The everyday place you'll hear it is with cars: the engine oil dipstick (and sometimes other fluids, depending on the vehicle).

You'll also see the word in other settings. Some quick tests use a small strip that you dip into a liquid and then check for a color change (for example, a urine dipstick test in a clinic). In these cases, "dipstick" points to the simple idea: dip it in, then read the result.

On top of the literal meaning, "dipstick" is also a mild, informal insult for a foolish or annoying person. It often comes out when someone is amused or fed up with a small mistake: "He forgot his wallet again—what a dipstick!" or "Don't be such a dipstick; the instructions are right there on the box!"

It's not a swear word, but it is still an insult, so the tone matters. Between friends it can sound like teasing; said to a stranger, it can sound rude. As with a lot of casual slang, it's best saved for informal moments with the right audience.