Longman Dictionary of Contemporary English - useful

~ adj 1 helping you to do or get what you want  (useful information | Dean's a really useful person to have around when things go wrong. | useful to sb)  (information that may be useful to the enemy | useful for sth)  (These yellow stickers are useful for leaving messages. | prove useful (=be useful in a particular situation))  (Clive's experience in the building trade proved useful for re-roofing the garage. | make yourself useful (=help someone))  (Can I do anything to make myself useful? | comein useful (=be useful in a particular situation))  (Keep that, it might come in useful later.) 2 BrE informal satisfactory  (The England cricket team scored quite a useful total.) - usefully adv