either of the two tides that occur at or just after new moon and full moon when the tide-generating force of the sun acts in the same direction as that of the moon, reinforcing it and causing the greatest rise and fall in tidal level. The highest spring tides (equinoctial springs) occur at the equinoxesCompare neap tide
A tide in which the difference between high and low tide is the greatest. Spring tides occur when the Moon is either new or full, and the Sun, the Moon, and the Earth are aligned. When this is the case, their collective gravitational pull on the Earth's water is strengthened. Compare neap tide. See more at tide.