Negatively Geared: This is where the borrowing / holding costs are greater than the rental income. So for example your rent is $700pm, but your rates, land tax, interest / gearing costs are $1000. This is said to be negatively geared by $300pm.
Positively Geared: Any property can be positively geared, it just depends how much cash deposit you contribute to it or how low the borrowings are against the property. So for example your rent is $700pm, but your rates, land tax, interest / gearing costs may be only $650pm, this is said to be positively geared by $50pm.
Positive Cash flow: This is where the income is greater than the expenses, regardless of gearing. Pretty much nearly every property has a positive cash flow if you don’t have any borrowings against it. Positive cash flow can be attained before tax or after. It basically means that there is a surplus of cash after expenses.
Negative Cash flow: This is where the outgoings are greater than the income [No gearing]. A term not often used, but a local example could be where the land tax, rates and maintenance exceed the rent, say like on an old property in Mosman that your retired Mum owns. So it is quite possible to have a negative cash flow property, but after Income tax is calculated the investment could become positively geared.