fiksrigardi

Read it from the right and it decodes itself. The main root of an Esperanto compound always comes last, so fiksrigardi is a kind of rigardi, looking, and fiksi, to fasten or to fix in place, tells you which kind: looking with the eyes fixed. That is exactly what English staring is, and English builds the same picture in a fixed gaze.

Note what happened to the joining vowel. The compound is fiks-rigardi, not fiksorigardi: the -i of fiksi drops and nothing replaces it, because ksr is pronounceable and Esperanto only inserts a linking -o- when the seam would be a mouthful. Compare piedpilko and naskiĝtago, which join bare, against skribotablo, a writing desk, where the -o- earns its keep.

And it is transitive, like the verb underneath it. You stare at something with a plain accusative and no preposition: li fiksrigardis la pordon, he stared at the door. Fiksrigardo is a stare as a thing you can give somebody, and fiksrigardanto is the person doing it. The nearest neighbours are gapi, to gawp with the mouth open, and miri, to be amazed, which is often why you were staring in the first place.