"More aggressive investors might keep a portion of their money in bonds to provide them with 'dry powder' that they can use when the stock market goes on sale."
Tony Robbins "Unshakeable" pg130
Firstly, what does dry powder mean?
According to Investopedia, "dry powder is a slang term referring to marketable securities that are highly liquid and considered cash-like. Dry powder can also refer to cash reserves kept on hand by a company, venture capital firm or person to cover future obligations, purchase assets or make acquisitions. Securities considered to be dry powder could be Treasuries, or other fixed income investments, and can be liquidated on short notice, in order to provide emergency funding or allow an investor to purchase assets."
In short, it refers to assets with high liquidity.
Why bonds instead of cash?
Bonds have cash-like liquidity. They earn higher interest rate than cash and can be converted to cash almost immediately.
The bond market is bigger than equity market. Bonds are for accredited investors, and they trade in large amounts. Bond trading is like stock trading, it is subject to supply and demand. You can sell before maturity in the market or hold it until maturity. In Singapore, bonds trade in min $250k, interest is normally paid semi-annually.