Upright the Nine of Wands is read as resilience, persistence and the guarded endurance of someone tested but not defeated; reversed, as exhaustion, paranoia, or a defensiveness that has hardened past the point of being useful.
This card is frequently distinguished, in practice, from the Seven of Wands, the suit's other defensive image: the Seven shows active defense of a position still being contested, where the Nine shows a defender who has already absorbed real damage and is now watching more warily than fighting outright. Readers commonly use the pairing to gauge how far into a difficult situation a querent already is, early defense against present pressure, or late endurance after damage already sustained.
Waite's own printed meaning, strength in reserve, a certain suspension of the fight, health and vigor tested but sound, is close to how most contemporary readers still describe the card, one of the more stable meanings in the deck across a century of reinterpretation, likely because Smith's picture is unusually specific and does most of the interpretive work itself.
Reversed, the wariness that serves the figure well upright becomes a liability, suspicion extended to people or circumstances that no longer pose the threat the figure is still braced against; readers frequently use this card, reversed, to ask a querent gently whether a guard raised for good reason is still necessary.