strange; odd; peculiar — a casual/colloquial way to say something is weird
彼の服は色の組み合わせがへんてこだ。
The combination of colors in his clothes is weird.
へんてこな音が夜中に聞こえてきた。
A strange noise was heard in the middle of the night.
へんてこな機械の使い方を教わった。
I was taught how to use a strange/odd machine.
a strange thing or person (used as a noun in casual speech)
あのへんてこは誰だろう、あまり近づきたくない。
Who is that odd person? I don't want to get too close.
こんなへんてこが作れるなんて驚いた。
I'm surprised someone could make such a strange thing.