Also means
sap
Usage Note
saper literally means to undermine the foundations of a structure (military engineering term). Figuratively it means to undermine authority, morale, or efforts (saper le moral des troupes). In informal French se saper or être sapé means to dress stylishly — a completely unrelated slang usage.
Examples
"Ces rumeurs sapent la confiance des équipes."
Natural Translation
These rumours undermine the teams' confidence.

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