I'm not familiar with the law and taxes in India but can provide guidance based on general accounting and tax principles.
You are right that receiving money as a loan is not income and isn't liable to income tax. Therefore i suggest you actually formalise this loan through a written contract with your friend. The contract should include all the usual elements of a loan: amount, interest (even if preferential or zero), principal, term, consequences of default and currency of loan.
You can then simply state the purpose of transfer as "Personal Loan Agreement". If you have such a document and are questioned by tax authorities you can easily show that the inward remittance is from a loan and should therefore be treated like any commercial loan for tax purposes. As long as you disclose the debt in your tax return (if required in India) and your friend discloses any interest received as income i think you'll be above board and won't be liable for any income tax.
To make sure, you might be better off having a quick consultation with an accountant or tax specialist in India to advise you and draft the loan agreement.