eye drop crush
A crush you don't wish to pursue. Either because you know it wouldn't be a good match or because they already have someone else. So you are happy just looking at them occasionally like eye drops that fill your eyes, but do nothing other than that.
A: Hey, you've been giving them looks for a while, will you ask them out
B: No, they're just an eye drop crush.
B: No, they're just an eye drop crush.