This is the 411th most frequent Turkish word.
güvenli
Safe.
The word 'güvenli' describes the built condition of the bridge, implying safety and stability.
Bu köprü çok güvenli bir şekilde inşa edilmiş.
This bridge was built very safely.
The word 'güvenli' is describing the neighborhood as a safe place for walking at night.
Geceleri bu mahallede yürümek oldukça güvenlidir.
Walking in this neighborhood at night is quite safe.
The word 'güvenli' modifies 'şifre', indicating the password should be protective and not easily breached.