In Polish, adding a prefix to a verb often changes its meaning in highly specific ways. The versatile prefix pod- (literally "under") is frequently used to mark an action that happens "under the radar." It gives verbs a sense of stealth, secrecy, or being done to a minor degree.
To talk about a character who frequently engages in these kinds of actions, you can use the adjective wścibski (nosy).
Stealthy Observations
When applied to verbs of perception or communication, pod- changes them into secretive or intrusive actions. For example, looking becomes spying (podglądać), asking becomes subtly fishing for information (podpytywać), and listening becomes eavesdropping (podsłuchiwać).
Secretive Actions and Misdeeds
This prefix is also used for physical actions done slyly, often entirely unnoticeably (niepostrzeżenie). Adding pod- creates verbs for secretly swapping things (podmienić), planting evidence or items (podrzucić), and stealthily stealing or pilfering (podkraść).
Diminished Actions
Beyond secrecy, pod- can also express doing an action just a little bit or to a minor degree. For example, turning a knob slightly to increase something is podkręcić, while eating small amounts on the side is podjadać.
Notice how podjadać perfectly combines both meanings of the pod- prefix: eating in small amounts, and often doing it secretly!