emotionless sex
When one or more characters involved in a sex act show boredom, disinterest, or no emotion at all.
Common signs are a deadpan expression, lack of blushing, or the character on the receiving end multitasking by doing other activities like reading or playing games at the same time.
Don't confuse this with empty eyes.
See also
The following tags are aliased to this tag: expressionless_sex (learn more).