Being of a suspicious nature:
— His suspiciousness destroyed his marriage.

synonym: suspicion.

Roget 487: incredulousness^†, incredulity; skepticism, pyrrhonism^†; want of faith etc. (irreligion) 989^†.    suspiciousness etc. adj.; scrupulosity; suspicion etc. (unbelief) 485.    mistrust, cynicism.    unbeliever, skeptic, cynic; misbeliever.   1, pyrrhonist; heretic etc. (heterodox) 984.    ... show more

Dutch: achterdocht
Polish: podejrzliwość