Passive-aggressive behaviour is a pattern of indirectly expressing negative feelings rather than dealing directly with issues and problems. The passive-aggressive person does not directly and openly express their negative thoughts and feelings. According the Mayo Clinic, there's a disconnect between what a passive-aggressive person says and what he or she does. They will often agree with someone when they are actually in disagreement, then act out negatively to the situation. The passive-aggressive person doesn't share their negative emotions verbally; they act them out through their behaviour. There are specific signs of passive-aggressive behaviour to watch for.
Listen for consistent complaining about being under appreciated. Since passive-aggressive people don't speak out when they are unhappy, they tend to develop a general attitude of victimisation, which will manifest itself in complaining.
Keep an eye out for irrational irritability. Passive-aggressive people will often become upset for no apparent reason. The real reason the passive-aggressive person is upset could be something that happened weeks, months or years ago.
Look for impatience and sullenness. Passive-aggressive people will be impatient and sullen because they internalise all perceived slights and offences.
Look for sabotaging behaviours. A passive-aggressive person will often take a project or responsibility on, even if he doesn't really want to, then sabotage it by being late, missing deadlines and generally doing a poor job.
Watch for signs of procrastination. Passive-aggressive people will often procrastinate as a way of silently protesting tasks they don't want to do.
Notice if the person seems inefficient. Another method of acting out passive-aggressively is inefficiency.
Look for signs of memory lapses. Passive-aggressive people will conveniently forget.