flukewarm

Generally: a random, warmish temperature, usually below the desired level.

Specifically: when one orders a hot drink (e.g. in a cafe) and finds it is not hot enough and at some arbitrary, warm-ish and disappointing temperature; then one may describe this drink as flukewarm. It is a portmanteau of fluke and lukewarm.

Leonidas: Man, I am so pissed. I was really looking forward to my morning coffee

Maximus: Why, what's wrong?
Leonidas: The drink is flukewarm. Damn.