adjective

1. of or containing seed or semen
2. of reproduction seminal power
3. like seed in being a source or a first stage in development; germinal; originative a seminal book
4. being the first or earliest of something that is later recognized as having been of primary influence a seminal jazz band
5. of essential importance; specif.,
   1. basic; central; principal
   2. crucial; critical; pivotal

Etymology: ME < MFr < L seminalis < semen (gen. seminis), a seed