1. noun /stɹeɪn/
There is a strain of madness in her family.
They say this years flu virus is a particularly virulent strain.
See Also: strew
2. verb /stɹeɪn/
So hauing said, her twixt her armes twaine / She straightly straynd, and colled tenderly [...].
b) To exert or struggle (to do something), especially to stretch (ones senses, faculties etc.) beyond what is normal or comfortable.
Relations between the United States and Guatemala traditionally have been close, although at times strained by human rights and civil/military issues.
Wikipedia foundation.