1. to make soil or land more fertile by adding nutrients or organic matter
Usage: British spelling; American English uses 'fertilize'
2. to cause an egg or plant to develop by introducing sperm or pollen
Usage: biological/reproductive context

Examples

• Farmers fertilise their fields every spring to improve crop yields.
• The gardener decided to fertilise the roses with compost.
• Bees fertilise flowers as they travel from plant to plant.
• The egg is fertilised when the sperm enters it.
• Regular rainfall and fertilising help the lawn stay green.
• They fertilise the vegetable garden with organic matter.