A "curate's egg" describes something that is mostly or partly bad, but partly good.
In its original context, the term refers to something that is obviously and essentially bad, but is euphemistically described as nonetheless having good features credited with undue redeeming power.
The term derives from a cartoon published in the humorous British magazine Punch on 9 November 1895. Drawn by George du Maurier and titled True Humility, it pictures a timid-looking curate eating breakfast in his bishop's house. The bishop says: "I'm afraid you've got a bad egg, Mr Jones." The curate replies, desperate not to offend his eminent host and ultimate employer: "Oh no, my Lord, I assure you that parts of it are excellent!" (This clearly cannot be true of a bad egg.)
The final issue of Punch, published in 1992, reprinted the cartoon with the caption: Curate: This f***ing egg's off! Thus Punch drew a contrast with the modern era, implying that younger people have little concern for the niceties of Victorian good manners towards those once considered their social superiors.
The following are some examples of actual usage of the term "curate's egg":
- "The past spring and summer season has seen much fluctuation. Like the curate's egg, it has been excellent in parts." 
- "All the same it is a curate's egg of a book. While the whole may be somewhat stale and addled, it would be unfair not to acknowledge the merits of some of its parts."
- "Like the curate's egg, the details of Wegener's hypothesis were good in parts."
- "Fishman... attempted a 'systematization' of SWH [Sapir-Whorf Hypothesis], suggesting that its extreme versions were untenable..., but that, like the curate's egg, it was excellent in parts."
- "The copper network is undoubtedly very good in parts, very poor in parts, and probably very adequate for most of it. But it is like any linear network: it will have good bits and bad bits... It's like the Curate's egg; it's good in parts." (Malcolm Turnbull, Australia Federal Communications Minister describing the state of the Telstra copper telecommunications network in 2015).
- "The commanding Rencher was rated a major plus in a curate's egg of a ballet".
- "The 14 February piece by James Mugg and Andrew Davies was like the curate’s egg: good in parts." 
- Paraphrase of definition in Collins Dictionary of the English Language, London, 1986, p.381
-  Oxford Dictionaries definition]
-  Cambridge Dictionaries definition]
- The New Oxford Dictionary of English. Oxford University Press. 1998. p. 449.
- van den Bergh, Hubert (2013). How to Sound Really Clever: 600 Words You Need to Know. A & C Black. p. 39. ISBN 1408194856.
- Minister's Gazette of Fashion, 1905.
- Oxford Magazine, 1962.
- John Gribbin, The Scientists, 2001.
- Philip K. Bock, "World view and language", in Encyclopedia of Linguistics, ed. William Bright, vol. 4, Oxford University Press, 1992, p. 250.
- big, risky project’: Turnbull says NBN cost will be settled soon. Crikey.com.au (2015-08-25). Retrieved on 2015-08-25.
- Antony Tudor's Shadowplay, 1967.
- Anonymous, "Derek Rencher, Ballet Dancer," obituary, Daily Telegraph (London), 11 February 2015.
- Geoff Slocombe https://www.aspistrategist.org.au/unmanned-naval-aviation-bigger-isnt-always-better/