| PSO | either of two muscles of the abdomen and pelvis that flex the trunk and rotate the thigh |
|---|---|
| PSO | small winged insect living on the bark and leaves of trees and feeding on e.g. fungi and decaying plant matter |
| PSO | a family of small soft-bodied insects that feed on decaying vegetation |
| PSO | an order of insects: includes booklice and barklice |
| PSO | small soft-bodied insect with chewing mouthparts and either no wings or two pairs |
| PSO | type genus of the Psophiidae: trumpeters |
| PSO | trumpeter of Brazil and Guiana |
| PSO | trumpeters |
| PSO | species of tropical Asian and African climbing herbs |
| PSO | tuberous-rooted twining annual vine bearing clusters of purplish flowers and pods with four jagged wings |
| PSO | widely distributed genus of herbs or shrubs with glandular compound leaves and spicate or racemose purple or white flowers |
| PSO | densely hairy perennial of central North America having edible tuberous roots |