Meanings according to Rider-Waite:
ASTROLOGICAL SIGNIFICANCE: Jupiter/Mars as a symbol of creative success; or the Saturn return, that is, its return to its point in the natal chart, as a sign of the beginning of a new period of life.
THREE OF DISKS Because of its black background, the Three of Disks is often considered an "unlucky card." However, on the contrary, it signifies a successfully passed examination, that is, a necessary and useful experience. Unlike the Eight of Disks, which personifies the Apprentice, the Three is already the Journeyman. Thus it shows that we have already ascended to a new level of knowledge, characterized not only by the desire to learn, but also by a certain amount of accumulated experience. This is the successful completion of a period of study or work, the transition into the next rank.
From the book: Hajo Banzhaf. THE TAROT HANDBOOK. Translated from German by E. Kolesov. Publisher: Center for Astrological Research, 1999.
THREE OF PENTACLES Work. The second decan of Capricorn, from January 1 to 9. Astrological equivalents: Leo, Mercury, the Sun, Venus, the conjunction of Mercury and the Sun. The second decan of Capricorn places emphasis on the individual activity of a person, his own self-improvement and professionalism. This decan is ruled by Mars, which directs one toward steady and persistent forward movement in fulfilling one's personal task. Dangerous for this decan is the attitude that "the end justifies the means," which prompts a person to close his eyes to the surrounding life until he attains his goal. And if the first decan is characterized by immersion in the very process of activity, the second, on the contrary, does not always understand that the process itself is only a part of personal accomplishments. Therefore, a person should not neglect the gifts of life, but should learn to enjoy their fruits and know how to take pleasure in them. In this, a person is helped by thought, which expands horizons and allows creative potential to manifest in full measure — hence the name of this decan, "Work." The ideal of work declares: do your work with love and perfection, for it is precisely love that imparts sanctity to labor. An uncreative approach, even to professional activity, deforms the personality, while self-admiration of one's own talent leads to the loss of results. Only when work becomes creativity are true achievements possible. The trap. Doing something without love and in a slipshod manner.
UPRIGHT POSITION In the upright position, the card symbolizes mastery, perfection, artistry, greatness, the possession of property, hierarchy, power. Moreover, power realized harmoniously, without coercion, the basis of which will most likely be financial interests. On the bodily level, the THREE OF PENTACLES may indicate pregnancy (as an additional factor), a change in weight, material acquisitions. In the THREE OF PENTACLES, the joint influence of such planets as Mercury and Venus is manifested, and all signs in which these planets are in any way expressed are involved. Mercurial harmony — a signed and certified document. Sometimes, marriage, but only in the presence of very strong other indicators; in this case, the most important thing will be the formal conclusion of the marriage. Contacts with financial bodies, with the law. The THREE gravitates toward perfection; therefore, the THREE OF PENTACLES may repeat the ACE OF PENTACLES, indicating great mastery shown by the subject of the card. (Most likely, this may concern trading or mediating operations.)
REVERSED POSITION In the reversed position, the THREE OF PENTACLES symbolizes stubbornness, cunning, poor quality of work or products, financial problems, divergence of thought, lack of professionalism — that is, Mercury and Venus manifest on a low level. Mercury acts especially strongly in the reversed THREE OF PENTACLES, which in some cases gives overwork and excessive workload "without respite." The reversed THREE OF PENTACLES may bring petty mischief.