Mamihlapinatapai: noun a look shared by two people each wishing that the other will initiate something that both desire but which neither one wants to start.

The word is from the Yaghan language, and its morphological structure is as follows:

mam- (reflexive/passive morph.) + -ihlapi- ‘to be at a loss as to what to do next’ + -n- (stative aspect affix) + -ata- (achievement affix) + -apai (dual, here reciprocal, marker).