An ideogram is a written sign that stands for an idea or a thing, not for the sound of a word. You look at the mark and you get the meaning, even if you cannot say the word in that language. The little figures on a toilet door — one for men, one for women — work a bit like this, and so do many signs at airports. Chinese characters are often called ideograms, though actually that is only half the story: some really do show an idea, but a great many also give a hint about the sound. People use the word in talk about writing, art, and design. It is a school-and-museum word, not a kitchen-table one.