chloroplast
This description fits the definition of a virus. Viruses are not considered living organisms because they lack the ability to carry out metabolic processes on their own and reproduce by invading host cells.
Avalanche
The prefix that fits the definition of backward or back is "re-".
"Frivolous" fits the definition of incapable of serious thought.
The prefix that fits the definition of pseudoscience is "pseudo-", which means false or not genuine.
Yes, it fits the definition
Para
Yes, Panama fits the definition of an isthmus.
Actively choose to engage, not disengage
Para is the prefix best fitting the definition of beside.
Guillotine.
a sweeping a floor