Bilateral eureka 

(This is the complete definition from my Ph.D. dissertation in 2003.)

"This is the Holy Grail of what, it seems, many daters are looking for. It's important that some "energy/feeling/connection" or "chemistry"

be present to develop rapport with a stranger. Habitual daters who are expecting to be swept off their feet with the next date may be missing this Eureka feeling by having unrealistic expectations. Many people seem to know in the first 15 minutes or so of a first meeting whether or not there is a future to the relationship, but it is hard to get to know a person that quickly. It's difficult for one person to be enchanted with the other person, and substantially more difficult for two strangers to both feel "eureka" when they meet the next stranger."

After having gone on lots of first blind dates over the last few months, he knew after just a few minutes that she was special. And she told him that she was just what she'd been looking for as well. It was as if the angels were singing when they met, and they both felt a rare and special warmth for each other that they hadn't felt on a first date in a long, long time. The sparks were there for both of them. They had found the elusive and wonderful "bilateral eureka" that makes people keep on dating until both have found that special, rare and amazing person. (Unless they've settled for someone less amazing!)

Bilateral eureka by Dr. RobertB, Ph.D. sexologist May 11, 2012