The proper glyph concept pertains to something cut into something or out of something as background; it is essentially of a 3-d phenomenon and makes no sense apart from it; the concept has nothing whatever to do with writing, which is almost never like that. A piece of lead type is indeed a glyph, and this is how you use it to print, but the printed text has no glyphs.
"Glyph" comes indeed from sculpting, so it was originally applied only to inscriptions carved in some durable material, like stone, wood or metal.
Nonetheless, nowadays it is a word commonly used when discussing typefaces (i.e. fonts), to designate the shape of a character, as opposed to its meaning. The same character, e.g. the Latin letter "A", can have various glyphs in different typefaces.
Before digital typography, the letters of a typeface were carved in metal by the typeface designer, so the term glyph was appropriate at that time.
Nowadays, it has persisted when used for typefaces drawn on computers, like other typographic terms, e.g. "font" referred to the process of casting molten metal into letter-shaped moulds.
In TFA the word glyph, actually geoglyph, is used in its original sense, not in the typographic sense, as it refers to geometric figures obtained by earth-working, so they are indeed in 3D, sculpted in earth.
As adrian points out, that is the etymology of the word, but not the sense in current use with digital fonts. So yes, the currently common sense for 'glyph' is about printed text.
I've noticed that Europeans users now comment at a higher frequency on HN than American users now, and set the tone of the site because of timezones.
Nonetheless, nowadays it is a word commonly used when discussing typefaces (i.e. fonts), to designate the shape of a character, as opposed to its meaning. The same character, e.g. the Latin letter "A", can have various glyphs in different typefaces.
Before digital typography, the letters of a typeface were carved in metal by the typeface designer, so the term glyph was appropriate at that time.
Nowadays, it has persisted when used for typefaces drawn on computers, like other typographic terms, e.g. "font" referred to the process of casting molten metal into letter-shaped moulds.
In TFA the word glyph, actually geoglyph, is used in its original sense, not in the typographic sense, as it refers to geometric figures obtained by earth-working, so they are indeed in 3D, sculpted in earth.