not thinking about the possible bad effects of your actions
Origin and usage
The adjective reckless has been used in English since the earliest days of the language. It is most likely a combination of an old verb, ‘reck’, meaning to pay heed to, and the suffix -less.
There are numerous English adjectives ending in ‘-less’, which carries the meaning ‘without’. Many of them have positive equivalents: ‘artless’ (artful), ‘careless’ (careful), ‘luckless’ (lucky) and so on. Reckless, like ‘gormless‘, is one of those that lacks a positive equivalent. In some cases the positive ‘pair’ used to exist but is no longer used much, if at all. This is the case of ‘feckless’, for example. In other cases the positive equivalent is used occasionally, especially for humorous effect; so someone might use the word ‘ruthful’ to say that a person or action was the opposite of ruthless. This applies to other adjectives as well: words such as ‘couth’, ‘kempt’ and ‘corrigible’ are used in contrast to their much more frequent negative equivalents, ‘uncouth‘, ‘unkempt‘ and ‘incorrigible‘, but are little used on their own. The concept of recklessness is used in the law. Reckless endangerment is behaviour that carries a risk of serious harm to others, while in US law, reckless driving is the crime of driving a vehicle in a way that is likely to hurt or kill people. In UK law this is called dangerous driving.
“Reckless youth makes rueful age.”
“Don’t be reckless with other people’s hearts. And don’t put up with people that are reckless with yours.”
impetuous, hasty, rash, impulsive