A disposal is the event in which you cease to own a crypto asset for tax purposes. Common examples include selling for fiat, swapping one token for another, spending crypto on goods/services, and in some jurisdictions certain gifts or transfers.
Not every wallet movement is a disposal (e.g. moving between your own wallets is often non-taxable), but classification depends on local guidance.
Why it matters: disposals are usually the trigger for capital gains or income calculations.
Educational definition — not tax advice. Rules vary by country.